KNOCKHARDY PUBLISHING ACIDS, BASES & SALTS National 5 Chemistry KNOCKHARDY PUBLISHING

ACIDS, BASES & SALTS www.knockhardy.org.uk INTRODUCTION This Powerpoint show is one of several produced to help students understand selected National 5 Chemistry topics. It is based on the requirements of the SQA specification but is suitable for other examination boards. Individual students may use the material at home for revision purposes and it can also prove useful for classroom teaching with an interactive white board. Accompanying notes on this, and the full range of Chemistry topics, are available from the KNOCKHARDY WEBSITE at... www.knockhardy.org.uk All diagrams and animations in this Powerpoint are original and created by Jonathan Hopton. Permission must be obtained for their use in any commercial work.

ACIDS, BASES & SALTS CONTENTS Acidity and alkalinity Indicators pH General methods for making salts Making salts from metal oxides Making salts from metal carbonates Making salts from metals Making salts from alkalis – by titration Making insoluble salts – by precipitation Questions

ACIDITY AND ALKALINITY • water is a neutral substance • when substances dissolve in water, the solution may become… ACIDIC or ALKALINE or stay NEUTRAL

ACIDITY AND ALKALINITY • water is a neutral substance • when substances dissolve in water, the solution may become… ACIDIC or ALKALINE or stay NEUTRAL • hydrogen ions H+(aq) make solutions acidic • hydroxide ions OH¯(aq) make solutions alkaline • solutions with equal numbers of H+(aq) and OH¯(aq) are neutral

INDICATORS • show by a colour change if a solution is acidic, alkaline or neutral • some can even show how acidic or how alkaline a solution is

INDICATORS • show by a colour change if a solution is acidic, alkaline or neutral • some can even show how acidic or how alkaline a solution is • well known indicators include…

INDICATORS • show by a colour change if a solution is acidic, alkaline or neutral • some can even show how acidic or how alkaline a solution is • well known indicators include… LITMUS acidic RED alkaline BLUE neutral PURPLE

INDICATORS • show by a colour change if a solution is acidic, alkaline or neutral • some can even show how acidic or how alkaline a solution is • well known indicators include… LITMUS acidic RED alkaline BLUE neutral PURPLE

INDICATORS • show by a colour change if a solution is acidic, alkaline or neutral • some can even show how acidic or how alkaline a solution is • well known indicators include… LITMUS acidic RED alkaline BLUE neutral PURPLE UNIVERSAL acidic RED alkaline VIOLET neutral GREEN

INDICATORS • show by a colour change if a solution is acidic, alkaline or neutral • some can even show how acidic or how alkaline a solution is • well known indicators include… LITMUS acidic RED alkaline BLUE neutral PURPLE UNIVERSAL acidic RED alkaline VIOLET neutral GREEN

pH SCALE

pH SCALE Used to compare the relative acidity (and alkalinity) of solutions. The value is related to the concentration of H+ions, in solution.

“The greater the concentration of hydrogen ions pH SCALE Used to compare the relative acidity (and alkalinity) of solutions. The value is related to the concentration of H+ions, in solution. “The greater the concentration of hydrogen ions in solution, the lower the pH”

“The greater the concentration of hydrogen ions pH SCALE Used to compare the relative acidity (and alkalinity) of solutions. The value is related to the concentration of H+ions, in solution. “The greater the concentration of hydrogen ions in solution, the lower the pH” <— 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 —> strongly weakly neutral weakly strongly acidic acidic alkaline alkaline

“The greater the concentration of hydrogen ions pH SCALE Used to compare the relative acidity (and alkalinity) of solutions. The value is related to the concentration of H+ions, in solution. “The greater the concentration of hydrogen ions in solution, the lower the pH” <— 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 —> strongly weakly neutral weakly strongly acidic acidic alkaline alkaline HCl CH3COOH H2O NH3 NaOH HYDROCHLORIC ETHANOIC AMMONIA SODIUM ACID ACID HYDROXIDE

“The greater the concentration of hydrogen ions pH SCALE Used to compare the relative acidity (and alkalinity) of solutions. The value is related to the concentration of H+ions, in solution. “The greater the concentration of hydrogen ions in solution, the lower the pH” <— 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 —> strongly weakly neutral weakly strongly acidic acidic alkaline alkaline HCl CH3COOH H2O NH3 NaOH HYDROCHLORIC ETHANOIC AMMONIA SODIUM ACID ACID HYDROXIDE Acidic solutions pH < 7 Alkaline solutions pH > 7 Neutral solutions pH = 7

pH SCALE Despite what some people think, the pH scale is not restricted to between 0 and 14. It extends beyond those values, but is not as relevant; e.g. the pH of the dilute HCl and H2SO4 found on the laboratory shelves is -0.3 and -0.6 respectively.

pH SCALE Despite what some people think, the pH scale is not restricted to between 0 and 14. It extends beyond those values, but is not as relevant; e.g. the pH of the dilute HCl and H2SO4 found on the laboratory shelves is -0.3 and -0.6 respectively. Weak acids have higher pH values than stronger ones of the same concentration. Ethanoic acid CH3COOH has a larger pH than hydrochloric acid HCl of the same concentration.

MEASURING pH Indicator Add a few drops of universal (full-range) indicator to the solution and compare the colour against a chart. The colour you “see” depends not only on how many drops of indicator you add but also on your perception of colour.

MEASURING pH Indicator Add a few drops of universal (full-range) indicator to the solution and compare the colour against a chart. The colour you “see” depends not only on how many drops of indicator you add but also on your perception of colour. pH meters Electrical/electronic devices which measure the conductivity of the solution. Having calibrated the apparatus against a solution of known pH, you place the probe in any solution and read off the pH value on a scale or digital read-out.

ACIDS

ACIDS Definition ACIDS ARE PROTON (H+ ion) DONORS Categories Acids can be arranged into groups according to how many H+ ions they produce from each molecule

THE ABOVE ARE MONOPROTIC (MONOBASIC) ACIDS Definition ACIDS ARE PROTON (H+ ion) DONORS Categories Acids can be arranged into groups according to how many H+ ions they produce from each molecule ACID SALTS ION EXAMPLE hydrochloric HCl chloride Cl¯ NaCl nitric HNO3 nitrate NO3¯ NaNO3 ethanoic CH3COOH ethanoate CH3COO¯ CH3COONa THE ABOVE ARE MONOPROTIC (MONOBASIC) ACIDS

ACIDS Definition ACIDS ARE PROTON (H+ ion) DONORS Categories Acids can be arranged into groups according to how many H+ ions they produce from each molecule ACID SALTS ION EXAMPLE hydrochloric HCl chloride Cl¯ NaCl nitric HNO3 nitrate NO3¯ NaNO3 ethanoic CH3COOH ethanoate CH3COO¯ CH3COONa THE ABOVE ARE MONOPROTIC (MONOBASIC)ACIDS sulphuric H2SO4 hydrogensulphate HSO4¯ NaHSO4 sulphate SO42- Na2SO4 “carbonic” H2CO3 hydrogencarbonate HCO3¯ NaHCO3 carbonate CO32- Na2CO3 THE ABOVE ARE DIPROTIC (DIBASIC)ACIDS

ACIDS Definition ACIDS ARE PROTON (H+ ion) DONORS Categories Acids can also arranged into groups according to the extent they split into ions when put in water.

ACIDS Definition ACIDS ARE PROTON (H+ ion) DONORS Categories Acids can also arranged into groups according to the extent they split into ions when put in water. STRONG ACIDS COMPLETELY dissociate (split up) into ions e.g. sulphuric, hydrochloric, nitric

ACIDS Definition ACIDS ARE PROTON (H+ ion) DONORS Categories Acids can also arranged into groups according to the extent they split into ions when put in water. STRONG ACIDS COMPLETELY dissociate (split up) into ions e.g. sulphuric, hydrochloric, nitric WEAK ACIDS PARTIALLY dissociate (split up) into ions e.g. ethanoic, citric, carbonic

ACIDS Definition ACIDS ARE PROTON (H+ ion) DONORS Categories Acids can also arranged into groups according to the extent they split into ions when put in water. STRONG ACIDS COMPLETELY dissociate (split up) into ions e.g. sulphuric, hydrochloric, nitric WEAK ACIDS PARTIALLY dissociate (split up) into ions e.g. ethanoic, citric, carbonic This means that if you take similar concentrations of HCl and CH3COOH, the concentration of H+ ions in the solution of CH3COOH will be less as only a few of its molecules will have split up into ions. Its pH will consequently be higher.

ACIDS Reactions The hydrogen ions produced by acids can be replaced by other positive ions (metal ions or ammonium ions) to produce salts. This occurs when dilute acids react with metals, oxides of metals, hydroxides of metals, carbonates, hydrogencarbonates and ammonia.

ACIDS Reactions The hydrogen ions produced by acids can be replaced by other positive ions (metal ions or ammonium ions) to produce salts. This occurs when dilute acids react with metals, oxides of metals, hydroxides of metals, carbonates, hydrogen carbonates and ammonia. HYDROCHLORIC ACID SODIUM HYDROXIDE AMMONIA SODIUM CHLORIDE AMMONIUM CHLORIDE ZINC COPPER OXIDE MAGNESIUM CARBONATE ZINC CHLORIDE COPPER CHLORIDE MAGNESIUM CHLORIDE

ACIDS Reactions The hydrogen ions produced by acids can be replaced by other positive ions (metal ions or ammonium ions) to produce salts. This occurs when dilute acids react with metals, oxides of metals, hydroxides of metals, carbonates, hydrogen carbonates and ammonia. SULPHURIC ACID SODIUM HYDROXIDE AMMONIA SODIUM SULPHATE AMMONIUM SULPHATE ZINC COPPER OXIDE MAGNESIUM CARBONATE ZINC SULPHATE COPPER SULPHATE MAGNESIUM SULPHATE

MAKING SALTS - POSSIBILITIES MIX SOLUTIONS OF TWO SUITABLE SALTS TO PRECIPITATE THE INSOLUBLE SALT IS THE SALT SOLUBLE OR INSOLUBLE? INSOLUBLE FILTER OFF THE SALT SOLUBLE ADD EXCESS METAL TO THE ACID THEN FILTER OFF THE EXCESS METAL DOES THE METAL REACT WITH DILUTE ACIDS? IS IT SAFE? YES YES NO NO ADD EXCESS METAL OXIDE OR METAL CARBONATE TO ACID THEN FILTER OFF THE EXCESS SOLID CRYSTALLISE THE SALT FROM THE FILTRATE NO IS THE METAL OXIDE OR CARBONATE SOLUBLE IN WATER? YES TITRATE THE METAL HYDROXIDE WITH ACID

PREPARATION OF SOLUBLE SALTS Salts can be made by NEUTRALISATION of acids; • acidic solutions contain aqueous hydrogen ions H+(aq) • sulphuric acid produces a sulphate • hydrochloric acid produces a chloride • nitric acid produces a nitrate

PREPARATION OF SOLUBLE SALTS Salts can be made by NEUTRALISATION of acids; • acidic solutions contain aqueous hydrogen ions H+(aq) • sulphuric acid produces a sulphate • hydrochloric acid produces a chloride • nitric acid produces a nitrate Other chemicals are formed, it depends on what is neutralising the acid. OXIDES SALT + WATER HYDROXIDES SALT + WATER CARBONATES SALT + CARBON DIOXIDE + WATER METALS SALT + HYDROGEN (not all metals are suitable; some are too reactive; others are not reactive enough)

PREPARATION OF SALTS BY NEUTRALISATION

MAKING SALTS – FROM INSOLUBLE BASES MIX SOLUTIONS OF TWO SUITABLE SALTS TO PRECIPITATE THE INSOLUBLE SALT IS THE SALT SOLUBLE OR INSOLUBLE? INSOLUBLE FILTER OFF THE SALT SOLUBLE ADD EXCESS METAL TO THE ACID THEN FILTER OFF THE EXCESS METAL DOES THE METAL REACT WITH DILUTE ACIDS? IS IT SAFE? YES YES NO NO ADD EXCESS METAL OXIDE OR METAL CARBONATE TO ACID THEN FILTER OFF THE EXCESS SOLID CRYSTALLISE THE SALT FROM THE FILTRATE NO IS THE METAL OXIDE OR CARBONATE SOLUBLE IN WATER? YES TITRATE THE METAL HYDROXIDE WITH ACID

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble oxide

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble oxide 1 Place dilute acid in a beaker and warm it gently without letting it boil (reactions are faster at higher temperatures)

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble oxide 1 Place dilute acid in a beaker and warm it gently without letting it boil (reactions are faster at higher temperatures) Remove the heat

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble oxide 1 Place dilute acid in a beaker and warm it gently without letting it boil (reactions are faster at higher temperatures) Remove the heat 3. Carefully and slowly add small amounts of the solid while stirring (most reactions of this type are exothermic i.e. they give off energy - the energy released would make the solution boil over)

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble oxide 1 Place dilute acid in a beaker and warm it gently without letting it boil (reactions are faster at higher temperatures) Remove the heat 3. Carefully and slowly add small amounts of the solid while stirring (most reactions of this type are exothermic i.e. they give off energy - the energy released would make the solution boil over) 4. Continue adding the solid until no more dissolves (this ensures all the acid has been used - it is easier to filter off excess solid than extract excess acid).

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble oxide 5. Filter the solution into an evaporating dish to remove excess solid

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble oxide 5. Filter the solution into an evaporating dish to remove excess solid Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation.

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble oxide 5. Filter the solution into an evaporating dish to remove excess solid Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation. When some of the water has been evaporated, let the solution to cool; (allows crystallisation takes place)

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble oxide 5. Filter the solution into an evaporating dish to remove excess solid Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation. When some of the water has been evaporated, let the solution to cool; (allows crystallisation takes place) When sufficient crystals have appeared, filter them off, wash with a little cold water and transfer them to a filter paper. Place another filter paper over the top and press gently to help remove some of the water.

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble oxide 5. Filter the solution into an evaporating dish to remove excess solid Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation. When some of the water has been evaporated, let the solution to cool; (allows crystallisation takes place) When sufficient crystals have appeared, filter them off, wash with a little cold water and transfer them to a filter paper. Place another filter paper over the top and press gently to help remove some of the water. 9. Allow the crystals to dry naturally in air. (heat can cause the crystals to decompose and lose their water of crystallisation)

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble carbonate

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble carbonate The method used is similar to that used with acids and metal oxides. The main differences is that it is not necessary to use heat and that carbon dioxide gas is given off so you have to make sure the solution doesn’t effervesce (fizz) too much.

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble carbonate The method used is similar to that used with acids and metal oxides. The main differences is that it is not necessary to use heat and that carbon dioxide gas is given off so you have to make sure the solution doesn’t effervesce (fizz) too much. Place dilute acid in a beaker

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble carbonate The method used is similar to that used with acids and metal oxides. The main differences is that it is not necessary to use heat and that carbon dioxide gas is given off so you have to make sure the solution doesn’t effervesce (fizz) too much. Place dilute acid in a beaker Carefully and slowly add small amounts of the solid carbonate while stirring – make sure there is not too much effervescence.

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble carbonate The method used is similar to that used with acids and metal oxides. The main differences is that it is not necessary to use heat and that carbon dioxide gas is given off so you have to make sure the solution doesn’t effervesce (fizz) too much. Place dilute acid in a beaker Carefully and slowly add small amounts of the solid carbonate while stirring – make sure there is not too much effervescence. 3. Continue adding the solid carbonate until no more dissolves (this ensures all the acid has been used - it is easier to filter off excess solid than extract excess acid).

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble carbonate 4. Filter the solution into an evaporating dish to remove excess solid

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble carbonate 4. Filter the solution into an evaporating dish to remove excess solid 5. Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation.

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble carbonate 4. Filter the solution into an evaporating dish to remove excess solid 5. Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation. 6. When some of the water has been evaporated, let the solution to cool; (allows crystallisation takes place)

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble carbonate 4. Filter the solution into an evaporating dish to remove excess solid 5. Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation. 6. When some of the water has been evaporated, let the solution to cool; (allows crystallisation takes place) 7. When sufficient crystals have appeared, filter them off, wash with a little cold water and transfer them to a filter paper. Place another filter paper over the top and press gently to help remove some of the water.

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess insoluble carbonate 4. Filter the solution into an evaporating dish to remove excess solid 5. Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation. 6. When some of the water has been evaporated, let the solution to cool; (allows crystallisation takes place) 7. When sufficient crystals have appeared, filter them off, wash with a little cold water and transfer them to a filter paper. Place another filter paper over the top and press gently to help remove some of the water. 8. Allow the crystals to dry naturally in air. (heat can cause the crystals to decompose and lose their water of crystallisation)

MAKING SALTS – FROM METALS MIX SOLUTIONS OF TWO SUITABLE SALTS TO PRECIPITATE THE INSOLUBLE SALT IS THE SALT SOLUBLE OR INSOLUBLE? INSOLUBLE FILTER OFF THE SALT SOLUBLE ADD EXCESS METAL TO THE ACID THEN FILTER OFF THE EXCESS METAL DOES THE METAL REACT WITH DILUTE ACIDS? IS IT SAFE? YES YES NO NO ADD EXCESS METAL OXIDE OR METAL CARBONATE TO ACID THEN FILTER OFF THE EXCESS SOLID CRYSTALLISE THE SALT FROM THE FILTRATE NO IS THE METAL OXIDE OR CARBONATE SOLUBLE IN WATER? YES TITRATE THE METAL HYDROXIDE WITH ACID

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess metal

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess metal The method used is similar to that used with acids and metal oxides or metal carbonates. However, because hydrogen is produced during the experiment, Bunsen burners must not be used while the chemical reaction is taking place. Not all metals are suitable: some are too reactive K, Na, Ca some don’t react Cu

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess metal The method used is similar to that used with acids and metal oxides or metal carbonates. However, because hydrogen is produced during the experiment, Bunsen burners must not be used while the chemical reaction is taking place. Not all metals are suitable: some are too reactive K, Na, Ca some don’t react Cu Place dilute acid in a beaker

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess metal The method used is similar to that used with acids and metal oxides or metal carbonates. However, because hydrogen is produced during the experiment, Bunsen burners must not be used while the chemical reaction is taking place. Not all metals are suitable: some are too reactive K, Na, Ca some don’t react Cu Place dilute acid in a beaker Carefully and slowly add small amounts of the metal while stirring – make sure there is not too much effervescence.

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess metal The method used is similar to that used with acids and metal oxides or metal carbonates. However, because hydrogen is produced during the experiment, Bunsen burners must not be used while the chemical reaction is taking place. Not all metals are suitable: some are too reactive K, Na, Ca some don’t react Cu Place dilute acid in a beaker Carefully and slowly add small amounts of the metal while stirring – make sure there is not too much effervescence. 3. Continue adding the metal until no more dissolves (this ensures all the acid has been used - it is easier to filter off excess metal than extract excess acid).

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess metal 4. Filter the solution into an evaporating dish to remove excess metal

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess metal 4. Filter the solution into an evaporating dish to remove excess metal 5. Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation.

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess metal 4. Filter the solution into an evaporating dish to remove excess metal 5. Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation. 6. When some of the water has been evaporated, let the solution to cool; (allows crystallisation takes place)

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess metal 4. Filter the solution into an evaporating dish to remove excess metal 5. Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation. 6. When some of the water has been evaporated, let the solution to cool; (allows crystallisation takes place) 7. When sufficient crystals have appeared, filter them off, wash with a little cold water and transfer them to a filter paper. Place another filter paper over the top and press gently to help remove some of the water.

PREPARATION OF SALTS BY NEUTRALISATION Acid with excess metal 4. Filter the solution into an evaporating dish to remove excess metal 5. Transfer the dish to a tripod and carefully warm the mixture to remove some of the water. Too much heat will drive off any water of crystallisation. 6. When some of the water has been evaporated, let the solution to cool; (allows crystallisation takes place) 7. When sufficient crystals have appeared, filter them off, wash with a little cold water and transfer them to a filter paper. Place another filter paper over the top and press gently to help remove some of the water. 8. Allow the crystals to dry naturally in air. (heat can cause the crystals to decompose and lose their water of crystallisation)

MAKING SALTS – FROM SOLUBLE BASES (ALKALIS) MIX SOLUTIONS OF TWO SUITABLE SALTS TO PRECIPITATE THE INSOLUBLE SALT IS THE SALT SOLUBLE OR INSOLUBLE? INSOLUBLE FILTER OFF THE SALT SOLUBLE ADD EXCESS METAL TO THE ACID THEN FILTER OFF THE EXCESS METAL DOES THE METAL REACT WITH DILUTE ACIDS? IS IT SAFE? YES YES NO NO ADD EXCESS METAL OXIDE OR METAL CARBONATE TO ACID THEN FILTER OFF THE EXCESS SOLID CRYSTALLISE THE SALT FROM THE FILTRATE NO IS THE METAL OXIDE OR CARBONATE SOLUBLE IN WATER? YES TITRATE THE METAL HYDROXIDE WITH ACID

ALKALIS

ALKALIS Definition ALKALIS ARE SOLUBLE BASES Their solutions contain hydroxide ions, OH¯(aq)

ALKALIS Definition ALKALIS ARE SOLUBLE BASES Their solutions contain hydroxide ions, OH¯(aq) STRONG ALKALIS sodium hydroxide (NaOH) potassium hydroxide (KOH) WEAK ALKALIS ammonia solution (ammonium hydroxide) (NH4OH)

ALKALIS Definition ALKALIS ARE SOLUBLE BASES Their solutions contain hydroxide ions, OH¯(aq) STRONG ALKALIS sodium hydroxide (NaOH) potassium hydroxide (KOH) WEAK ALKALIS ammonia solution (ammonium hydroxide) (NH4OH) Making salts using alkalis cannot be done by the methods used for insoluble bases because you cannot tell when all the acid has been neutralised – the excess alkali is soluble.

ALKALIS Definition ALKALIS ARE SOLUBLE BASES Their solutions contain hydroxide ions, OH¯(aq) STRONG ALKALIS sodium hydroxide (NaOH) potassium hydroxide (KOH) WEAK ALKALIS ammonia solution (ammonium hydroxide) (NH4OH) Making salts using alkalis cannot be done by the methods used for insoluble bases because you cannot tell when all the acid has been neutralised – the excess alkali is soluble. The salts are made by titration using an indicator ACID + ALKALINE HYDROXIDE ——> NEUTRAL SALT + WATER SOLUTION SOLUTION

The indicator tells you when the acid has been neutralised ALKALIS Definition ALKALIS ARE SOLUBLE BASES Their solutions contain hydroxide ions, OH¯(aq) STRONG ALKALIS sodium hydroxide (NaOH) potassium hydroxide (KOH) WEAK ALKALIS ammonia solution (ammonium hydroxide) (NH4OH) Making salts using alkalis cannot be done by the methods used for insoluble bases because you cannot tell when all the acid has been neutralised – the excess alkali is soluble. The salts are made by titration using an indicator ACID + ALKALINE HYDROXIDE ——> NEUTRAL SALT + WATER SOLUTION SOLUTION The indicator tells you when the acid has been neutralised

AMMONIUM SALTS Ammonia is very soluble in water giving an alkaline solution which can be neutralised by acids to produce AMMONIUM SALTS e.g. AMMONIA + HYDROCHLORIC —> AMMONIUM SOLUTION ACID CHLORIDE

Ammonium salts make very important fertilisers Ammonia is very soluble in water giving an alkaline solution which can be neutralised by acids to produce AMMONIUM SALTS e.g. AMMONIA + HYDROCHLORIC —> AMMONIUM SOLUTION ACID CHLORIDE If ammonium hydroxide is specified you can write the equation AMMONIUM + HYDROCHLORIC —> AMMONIUM + WATER HYDROXIDE ACID CHLORIDE Ammonium salts make very important fertilisers

MAKING SALTS BY TITRATION This method is limited to the soluble salts of ammonia or alkali metals e.g. ammonium chloride NH4Cl sodium chloride NaCl potassium sulphate K2SO4 sodium nitrate NaNO3

MAKING SALTS BY TITRATION This method is limited to the soluble salts of ammonia or alkali metals e.g. ammonium chloride NH4Cl sodium chloride NaCl potassium sulphate K2SO4 sodium nitrate NaNO3 Method React an acid with an alkali (hydroxides of Group I metals and ammonia). The method involves TITRATION.

MAKING SALTS BY TITRATION This method is limited to the soluble salts of ammonia or alkali metals e.g. ammonium chloride NH4Cl sodium chloride NaCl potassium sulphate K2SO4 sodium nitrate NaNO3 Method React an acid with an alkali (hydroxides of Group I metals and ammonia). The method involves TITRATION. 1 Place a measured quantity of acid in a conical flask. 2 Add three or four drops of a suitable indicator. 3 Place the alkali in a burette. Note the level of the liquid. 4 Add the alkali to the acid until the indicator just changes colour Note the new level of liquid. 5 Repeat experiment with exactly the same volumes but no indicator. 6 Evaporate a small amount of the water in an evaporating basin and let the solution cool to allow crystals to form.

MAKING SALTS BY TITRATION This method is limited to the soluble salts of ammonia or alkali metals e.g. ammonium chloride NH4Cl sodium chloride NaCl potassium sulphate K2SO4 sodium nitrate NaNO3 Method React an acid with an alkali (hydroxides of Group I metals and ammonia). The method involves TITRATION. 1 Place a measured quantity of acid in a conical flask. 2 Add three or four drops of a suitable indicator. 3 Place the alkali in a burette. Note the level of the liquid. 4 Add the alkali to the acid until the indicator just changes colour Note the new level of liquid. 5 Repeat experiment with exactly the same volumes but no indicator. 6 Evaporate a small amount of the water in an evaporating basin and let the solution cool to allow crystals to form.

MAKING SALTS BY TITRATION This method is limited to the soluble salts of ammonia or alkali metals e.g. ammonium chloride NH4Cl sodium chloride NaCl potassium sulphate K2SO4 sodium nitrate NaNO3 Method React an acid with an alkali (hydroxides of Group I metals and ammonia). The method involves TITRATION. 1 Place a measured quantity of acid in a conical flask. 2 Add three or four drops of a suitable indicator. 3 Place the alkali in a burette. Note the level of the liquid. 4 Add the alkali to the acid until the indicator just changes colour Note the new level of liquid. 5 Repeat experiment with exactly the same volumes but no indicator. 6 Evaporate a small amount of the water in an evaporating basin and let the solution cool to allow crystals to form.

MAKING SALTS BY TITRATION This method is limited to the soluble salts of ammonia or alkali metals e.g. ammonium chloride NH4Cl sodium chloride NaCl potassium sulphate K2SO4 sodium nitrate NaNO3 Method React an acid with an alkali (hydroxides of Group I metals and ammonia). The method involves TITRATION. 1 Place a measured quantity of acid in a conical flask. 2 Add three or four drops of a suitable indicator. 3 Place the alkali in a burette. Note the level of the liquid. 4 Add the alkali to the acid until the indicator just changes colour Note the new level of liquid. 5 Repeat experiment with exactly the same volumes but no indicator. 6 Evaporate a small amount of the water in an evaporating basin and let the solution cool to allow crystals to form.

MAKING SALTS BY TITRATION This method is limited to the soluble salts of ammonia or alkali metals e.g. ammonium chloride NH4Cl sodium chloride NaCl potassium sulphate K2SO4 sodium nitrate NaNO3 Method React an acid with an alkali (hydroxides of Group I metals and ammonia). The method involves TITRATION. 1 Place a measured quantity of acid in a conical flask. 2 Add three or four drops of a suitable indicator. 3 Place the alkali in a burette. Note the level of the liquid. 4 Add the alkali to the acid until the indicator just changes colour Note the new level of liquid. 5 Repeat experiment with exactly the same volumes but no indicator. 6 Evaporate a small amount of the water in an evaporating basin and let the solution cool to allow crystals to form.

MAKING SALTS BY TITRATION This method is limited to the soluble salts of ammonia or alkali metals e.g. ammonium chloride NH4Cl sodium chloride NaCl potassium sulphate K2SO4 sodium nitrate NaNO3 Method React an acid with an alkali (hydroxides of Group I metals and ammonia). The method involves TITRATION. 1 Place a measured quantity of acid in a conical flask. 2 Add three or four drops of a suitable indicator. 3 Place the alkali in a burette. Note the level of the liquid. 4 Add the alkali to the acid until the indicator just changes colour Note the new level of liquid. 5 Repeat experiment with exactly the same volumes but no indicator. 6 Evaporate a small amount of the water in an evaporating basin and let the solution cool to allow crystals to form.

MAKING SALTS BY TITRATION This method is limited to the soluble salts of ammonia or alkali metals e.g. ammonium chloride NH4Cl sodium chloride NaCl potassium sulphate K2SO4 sodium nitrate NaNO3 Method React an acid with an alkali (hydroxides of Group I metals and ammonia). The method involves TITRATION. 1 Place a measured quantity of acid in a conical flask. 2 Add three or four drops of a suitable indicator. 3 Place the alkali in a burette. Note the level of the liquid. 4 Add the alkali to the acid until the indicator just changes colour Note the new level of liquid. 5 Repeat experiment with exactly the same volumes but no indicator. 6 Evaporate a small amount of the water in an evaporating basin and let the solution cool to allow crystals to form.

MAKING SALTS BY TITRATION Example word equations:- sodium hydroxide + hydrochloric acid —> sodium chloride + water sodium hydroxide + sulphuric acid —> sodium sulphate + water potassium hydroxide + nitric acid —> potassium nitrate + water ammonium hydroxide + nitric acid —> ammonium nitrate + water

MAKING SALTS BY TITRATION Example word equations:- sodium hydroxide + hydrochloric acid —> sodium chloride + water sodium hydroxide + sulphuric acid —> sodium sulphate + water potassium hydroxide + nitric acid —> potassium nitrate + water ammonium hydroxide + nitric acid —> ammonium nitrate + water Now complete these:-

MAKING SALTS BY TITRATION Example word equations:- sodium hydroxide + hydrochloric acid —> sodium chloride + water sodium hydroxide + sulphuric acid —> sodium sulphate + water potassium hydroxide + nitric acid —> potassium nitrate + water ammonium hydroxide + nitric acid —> ammonium nitrate + water Now complete these:- potassium hydroxide + hydrochloric acid —> potassium chloride + water

MAKING SALTS BY TITRATION Example word equations:- sodium hydroxide + hydrochloric acid —> sodium chloride + water sodium hydroxide + sulphuric acid —> sodium sulphate + water potassium hydroxide + nitric acid —> potassium nitrate + water ammonium hydroxide + nitric acid —> ammonium nitrate + water Now complete these:- potassium hydroxide + hydrochloric acid —> potassium chloride + water sodium hydroxide + nitric acid —> sodium nitrate + water

MAKING SALTS BY TITRATION Example word equations:- sodium hydroxide + hydrochloric acid —> sodium chloride + water sodium hydroxide + sulphuric acid —> sodium sulphate + water potassium hydroxide + nitric acid —> potassium nitrate + water ammonium hydroxide + nitric acid —> ammonium nitrate + water Now complete these:- potassium hydroxide + hydrochloric acid —> potassium chloride + water sodium hydroxide + nitric acid —> sodium nitrate + water ammonium hydroxide + hydrochloric acid —> ammonium chloride + water

MAKING SALTS BY TITRATION Example word equations:- sodium hydroxide + hydrochloric acid —> sodium chloride + water sodium hydroxide + sulphuric acid —> sodium sulphate + water potassium hydroxide + nitric acid —> potassium nitrate + water ammonium hydroxide + nitric acid —> ammonium nitrate + water Now complete these:- potassium hydroxide + hydrochloric acid —> potassium chloride + water sodium hydroxide + nitric acid —> sodium nitrate + water ammonium hydroxide + hydrochloric acid —> ammonium chloride + water

NEUTRALISATION - IONIC EQUATION In all alkali – acid reactions, the same ionic reaction takes place…

NEUTRALISATION - IONIC EQUATION In all alkali – acid reactions, the same ionic reaction takes place… sodium hydroxide + dil. nitric acid —> sodium nitrate + water NaOH(aq) + HNO3 (aq) —> NaNO3 (aq) + H2O (l)

NEUTRALISATION - IONIC EQUATION In all alkali – acid reactions, the same ionic reaction takes place… sodium hydroxide + dil. nitric acid —> sodium nitrate + water NaOH(aq) + HNO3 (aq) —> NaNO3 (aq) + H2O (l) Na+(aq) + OH¯(aq) + H+(aq) + NO3¯(aq) —> Na+(aq) + NO3¯(aq) + H2O(l)

NEUTRALISATION - IONIC EQUATION In all alkali – acid reactions, the same ionic reaction takes place… sodium hydroxide + dil. nitric acid —> sodium nitrate + water NaOH(aq) + HNO3 (aq) —> NaNO3 (aq) + H2O (l) Na+(aq) + OH¯(aq) + H+(aq) + NO3¯(aq) —> Na+(aq) + NO3¯(aq) + H2O(l) cancel ions H+(aq) + OH¯(aq) —> H2O(l) from from acid alkali

MAKING SALTS - POSSIBILITIES MIX SOLUTIONS OF TWO SUITABLE SALTS TO PRECIPITATE THE INSOLUBLE SALT IS THE SALT SOLUBLE OR INSOLUBLE? INSOLUBLE FILTER OFF THE SALT SOLUBLE ADD EXCESS METAL TO THE ACID THEN FILTER OFF THE EXCESS METAL DOES THE METAL REACT WITH DILUTE ACIDS? IS IT SAFE? YES YES NO NO ADD EXCESS METAL OXIDE OR METAL CARBONATE TO ACID THEN FILTER OFF THE EXCESS SOLID CRYSTALLISE THE SALT FROM THE FILTRATE NO IS THE METAL OXIDE OR CARBONATE SOLUBLE IN WATER? YES TITRATE THE METAL HYDROXIDE WITH ACID

PREPARATION OF INSOLUBLE SALTS

PREPARATION OF INSOLUBLE SALTS METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed.

PREPARATION OF INSOLUBLE SALTS METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. EXAMPLES silver chloride silver nitrate and sodium chloride barium sulphate barium chloride and sodium sulphate lead iodide lead nitrate and potassium iodide

PREPARATION OF INSOLUBLE SALTS PREPARATION OF SILVER CHLORIDE METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. PREPARATION OF SILVER CHLORIDE To make silver chloride you need… (i) a soluble silver salt silver nitrate plus (ii) a soluble chloride sodium chloride.

PREPARATION OF INSOLUBLE SALTS PREPARATION OF SILVER CHLORIDE METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. PREPARATION OF SILVER CHLORIDE To make silver chloride you need… (i) a soluble silver salt silver nitrate plus (ii) a soluble chloride sodium chloride. 1 Prepare a solution of sodium chloride.

PREPARATION OF INSOLUBLE SALTS PREPARATION OF SILVER CHLORIDE METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. PREPARATION OF SILVER CHLORIDE To make silver chloride you need… (i) a soluble silver salt silver nitrate plus (ii) a soluble chloride sodium chloride. 2 The sodium chloride lattice breaks up and dissolves in the water.

PREPARATION OF INSOLUBLE SALTS PREPARATION OF SILVER CHLORIDE METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. PREPARATION OF SILVER CHLORIDE To make silver chloride you need… (i) a soluble silver salt silver nitrate plus (ii) a soluble chloride sodium chloride. 3 Prepare a solution of silver nitrate.

PREPARATION OF INSOLUBLE SALTS PREPARATION OF SILVER CHLORIDE METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. PREPARATION OF SILVER CHLORIDE To make silver chloride you need… (i) a soluble silver salt silver nitrate plus (ii) a soluble chloride sodium chloride. 4 The silver nitrate lattice breaks up and dissolves in the water.

PREPARATION OF INSOLUBLE SALTS PREPARATION OF SILVER CHLORIDE METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. PREPARATION OF SILVER CHLORIDE To make silver chloride you need… (i) a soluble silver salt silver nitrate plus (ii) a soluble chloride sodium chloride. 5 Mix the two solutions.

PREPARATION OF INSOLUBLE SALTS PREPARATION OF SILVER CHLORIDE METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. PREPARATION OF SILVER CHLORIDE To make silver chloride you need… (i) a soluble silver salt silver nitrate plus (ii) a soluble chloride sodium chloride. 6 All four ions are now mixed together.

PREPARATION OF INSOLUBLE SALTS PREPARATION OF SILVER CHLORIDE METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. PREPARATION OF SILVER CHLORIDE To make silver chloride you need… (i) a soluble silver salt silver nitrate plus (ii) a soluble chloride sodium chloride. 7 The silver ions and chloride ions come together and the insoluble silver chloride forms a white precipitate.

PREPARATION OF INSOLUBLE SALTS PREPARATION OF SILVER CHLORIDE METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. PREPARATION OF SILVER CHLORIDE To make silver chloride you need… (i) a soluble silver salt silver nitrate plus (ii) a soluble chloride sodium chloride. 7 Because sodium nitrate is soluble in water their ions remain in solution. The precipitate is then filtered, washed and dried.

PREPARATION OF INSOLUBLE SALTS PREPARATION OF SILVER CHLORIDE METHOD Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed. PREPARATION OF SILVER CHLORIDE To make silver chloride you need… (i) a soluble silver salt silver nitrate plus (ii) a soluble chloride sodium chloride.

SALTS - QUESTIONS

SALTS - QUESTIONS 1. Work out what you get if the following chemicals are mixed. a) zinc and sulphuric acid b) copper carbonate and nitric acid c) sodium hydroxide and hydrochloric acid d) lead oxide and nitric acid e) magnesium and hydrochloric acid f) ammonium hydroxide and sulphuric acid g) magnesium carbonate and sulphuric acid

SALTS - QUESTIONS 1. Work out what you get if the following chemicals are mixed. a) zinc and sulphuric acid zinc sulphate + hydrogen b) copper carbonate and nitric acid copper nitrate + carbon dioxide + water c) sodium hydroxide and hydrochloric acid sodium chloride + water d) lead oxide and nitric acid lead nitrate + water e) magnesium and hydrochloric acid magnesium chloride + hydrogen f) ammonium hydroxide and sulphuric acid ammonium sulphate + water g) magnesium carbonate and sulphuric acid magnesium + carbon + water sulphate dioxide

SALTS - QUESTIONS 1. Work out what you get if the following chemicals are mixed. a) zinc and sulphuric acid zinc sulphate + hydrogen b) copper carbonate and nitric acid copper nitrate + carbon dioxide + water c) sodium hydroxide and hydrochloric acid sodium chloride + water d) lead oxide and nitric acid lead nitrate + water e) magnesium and hydrochloric acid magnesium chloride + hydrogen f) ammonium hydroxide and sulphuric acid ammonium sulphate + water g) magnesium carbonate and sulphuric acid magnesium + carbon + water sulphate dioxide 2. Answer the following... Which ion is found in (i) acidic solutions; H+(aq) (ii) alkaline solutions? What is formed when you mix these two ions together? What name do we give to this type of reaction? When making salts from metals, oxides and carbonates, how do you know when all the acid is used up? When making salts from soluble Group I hydroxides, what do you use to check when all the acid is used up?

SALTS - QUESTIONS 1. Work out what you get if the following chemicals are mixed. a) zinc and sulphuric acid zinc sulphate + hydrogen b) copper carbonate and nitric acid copper nitrate + carbon dioxide + water c) sodium hydroxide and hydrochloric acid sodium chloride + water d) lead oxide and nitric acid lead nitrate + water e) magnesium and hydrochloric acid magnesium chloride + hydrogen f) ammonium hydroxide and sulphuric acid ammonium sulphate + water g) magnesium carbonate and sulphuric acid magnesium + carbon + water sulphate dioxide 2. Answer the following... Which ion is found in (i) acidic solutions; H+(aq) (ii) alkaline solutions? OH¯(aq) What is formed when you mix these two ions together? WATER What name do we give to this type of reaction? NEUTRALISATION When making salts from metals, oxides and carbonates, how do you know when all the acid is used up? WHEN THE SOLID NO LONGER DISSOLVES When making salts from soluble Group I hydroxides, what do you use to check when all the acid is used up? AN INDICATOR

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