ACIDS & BASES EQ: Why are some aqueous solutions acidic, others basic, and some neutral? What makes them that way? GPS: SC7. Students will characterize the properties that describe solutions and the nature of acids and bases. b. Compare, contrast, and evaluate the nature of acids and bases: Arrhenius, Bronsted-Lowry Acid/Bases Arrhenius, Bronsted-Lowry Acid/Bases Strong vs. weak acids/bases in terms of percent dissociation Strong vs. weak acids/bases in terms of percent dissociation Hydronium ion concentration Hydronium ion concentration pH pH Acid-Base neutralization Acid-Base neutralization

The Theory of Ionization Many substances form ions when dissolved in water.

Acids (Arrhenius’ Definition) Acids form hydrogen ions ( H+ )when dissolved in water

Acids (Arrhenius’ Modified) Acids form hydronium ions ( H 3 O + ) when dissolved in water

HCl +H 2 O  H 2 SO 4 +2H 2 O  H 3 O + + Cl - 2H 3 O + + SO 4 -2

Common Acids HCl Hydrochloric HCl Hydrochloric H 2 SO 4 Sulfuric H 2 SO 4 Sulfuric HNO 3 Nitric HNO 3 Nitric H 3 PO 4 Phosphoric H 3 PO 4 Phosphoric H 2 CO 3 Carbonic H 2 CO 3 Carbonic

ACIDS ACID: a chemical that produces hydronium ions (H 3 O +1 ) when dissolved in water ACID: a chemical that produces hydronium ions (H 3 O +1 ) when dissolved in water Acids are ionic compounds ( a compound with a positive or negative charge) that break apart in water to form a hydrogen ion (H+). Acids are ionic compounds ( a compound with a positive or negative charge) that break apart in water to form a hydrogen ion (H+). H 3 O +1 is just a hydrogen ion joined to a water molecule. H 3 O +1 is just a hydrogen ion joined to a water molecule. Hydrogen is always the first element in the acid formula Hydrogen is always the first element in the acid formula HCl + H 2 O  H +1 + Cl -1 + H 2 O  H 3 O +1 + Cl -1 HCl + H 2 O  H +1 + Cl -1 + H 2 O  H 3 O +1 + Cl -1 (H +1 is an acidic hydrogen or proton) (H +1 is an acidic hydrogen or proton) H +1 is used to mean the same as H 3 O +1 H +1 is used to mean the same as H 3 O +1 H +1 = H 3 O +1 H +1 = H 3 O +1

ACIDS Properties: Properties: Sour taste (vinegar—acetic acid, lemons— citric acid) Sour taste (vinegar—acetic acid, lemons— citric acid) Are electrolytes (compounds that conduct electricity) Are electrolytes (compounds that conduct electricity) React w/ metals to form H 2 gas; React w/most metals to corrode them (Strong acids are dangerous and can burn your skin). React w/ metals to form H 2 gas; React w/most metals to corrode them (Strong acids are dangerous and can burn your skin). Change indicator colors (blue to red) Change indicator colors (blue to red) React w/ carbonates (CO 3 -2 ) to form CO 2. React w/ carbonates (CO 3 -2 ) to form CO 2. React w/or neutralize bases to form salt & water React w/or neutralize bases to form salt & water Produces H + ions in water Produces H + ions in water pH<7 pH<7

Bases (Arrhenius’ Definition) Bases form hydroxide ions ( OH- )when dissolved in water

NaOH +H 2 O  Na + + OH - + H 2 O Mg(OH) 2 +H 2 O  Mg OH - + H 2 O

Common Bases NaOH Sodium Hydroxide NaOH Sodium Hydroxide NH 4 OH Ammonium Hyd. NH 4 OH Ammonium Hyd. Ca(OH) 2 Calcium Hydrox. Ca(OH) 2 Calcium Hydrox.

BASES- AKA: alkalis Base: chemical that produces hydroxide ions (OH -1 ) when dissolved in water. Base: chemical that produces hydroxide ions (OH -1 ) when dissolved in water. Bases are ionic compounds that break apart to form a negatively charged hydroxide ion (OH-) in water. Bases are ionic compounds that break apart to form a negatively charged hydroxide ion (OH-) in water. The strength of a base is determined by the concentration of Hydroxide ions (OH-). The greater the concentration of OH- ions the stronger the base. The strength of a base is determined by the concentration of Hydroxide ions (OH-). The greater the concentration of OH- ions the stronger the base. Two kinds of bases: Two kinds of bases: 1. Ionic bases (Metal hydroxides: alkali & alkaline- earth metals) 1. Ionic bases (Metal hydroxides: alkali & alkaline- earth metals) NaOH  Na +1 + OH -1 NaOH  Na +1 + OH Covalent bases that accept H +1 from water (NH 3 = ammonia) 2. Covalent bases that accept H +1 from water (NH 3 = ammonia) NH 3 + H 2 O  NH OH -1 NH 3 + H 2 O  NH OH -1

BASES: properties Bitter taste Bitter taste Feel slippery Feel slippery Are electrolytes Are electrolytes Do not react with most metals Do not react with most metals Change indicator colors (red to blue) Change indicator colors (red to blue) React w/ or neutralize acids to produce salt & water React w/ or neutralize acids to produce salt & water Produce OH - in water Produce OH - in water To name: name the metal & hydroxide To name: name the metal & hydroxide pH>7 pH>7 Strong bases are very dangerous and can burn your skin Strong bases are very dangerous and can burn your skin

Acid-Base Indicators Dye that changes color in the presence of an acid or base Dye that changes color in the presence of an acid or base Example: Litmus paper (red when an acid is present; blue when a base is present) Example: Litmus paper (red when an acid is present; blue when a base is present) Example: Red cabbage juice (pink when an acid is present; purple/blue when a base is present Example: Red cabbage juice (pink when an acid is present; purple/blue when a base is present

Acids and Bases (Bronsted-Lowry Def’n) Acid -proton (H+) donor Base -proton (H+) acceptor

Naming Acids Binary acids (2 ions) – begin with the prefix hydro, the root name of the element, and the suffix -ic Binary acids (2 ions) – begin with the prefix hydro, the root name of the element, and the suffix -ic To name: Look at ending: To name: Look at ending: -ate polyatomic ions  -ic acids -ate polyatomic ions  -ic acids -ite polyatomic ions  -ous acids -ite polyatomic ions  -ous acids -ide monatomic ions  hydro –ic acid -ide monatomic ions  hydro –ic acid Monoprotic acid: Has one acidic hydrogen, like HCl Monoprotic acid: Has one acidic hydrogen, like HCl Diprotic acid: Has two acidic hydrogens, like H 2 SO 4 Diprotic acid: Has two acidic hydrogens, like H 2 SO 4 Triprotic acid: Has three acidic hydrogens, like H 3 PO 4 Triprotic acid: Has three acidic hydrogens, like H 3 PO 4 Acids containing more oxygen than the common form are named by adding the prefix per to the common name. Acids containing more oxygen than the common form are named by adding the prefix per to the common name. acid containing fewer oxygen atoms is given the prefix hypo and the suffix -ous acid containing fewer oxygen atoms is given the prefix hypo and the suffix -ous

Naming Acids Per – ROOT – ic More oxygen ROOT – ic Most common ROOT – ous Less oxygen Hypo – ROOT – ous Still less oxygen

Common Bases/ Names NaOH Sodium Hydroxide NaOH Sodium Hydroxide NH 4 OH Ammonium Hyd. NH 4 OH Ammonium Hyd. Ca(OH) 2 Calcium Hydrox. Ca(OH) 2 Calcium Hydrox. Naming Bases: Naming Bases: Name the cation; name the anion Name the cation; name the anion

Ionization of Acids and Bases When in water, solid acid and base compounds dissolve and ionize (or dissociate) When in water, solid acid and base compounds dissolve and ionize (or dissociate) Ionize: Break up into ions that float freely in solution; can then conduct electricity. Ionize: Break up into ions that float freely in solution; can then conduct electricity. Strong acids & bases ionize/dissociates completely, every molecule separates into ions. Strong acids & bases ionize/dissociates completely, every molecule separates into ions. Strong acid: Strong acid: HCl + H 2 O  H +1 + Cl -1 + H 2 O  H 3 O +1 + Cl -1 HCl + H 2 O  H +1 + Cl -1 + H 2 O  H 3 O +1 + Cl -1 Strong base: NaOH  Na +1 + OH -1 Strong base: NaOH  Na +1 + OH -1 Weak acids & bases do not ionize completely when dissolved in water Weak acids & bases do not ionize completely when dissolved in water

Common strong acids & bases Common strong acids Common strong bases Perchloric acid, Lithium hydroxide, LiOH Sulfuric acid, H 2 SO 4 Sodium hydroxide, NaOH Hydroiodic acid, HI Potassium hydroxide, KOH Hydrobromic acid, HBr Calcium hydroxide, Ca(OH) 2 Hydrochloric acid, HCl Barium hydroxide, Ba(OH) 2 Nitric acid, HNO 3 Magnesium hydroxide, Mg(OH) 2

The pH Scale pH = - log [H 3 O + ] acid neutral base

pH Scale used to express the acidity of a solution. Scale used to express the acidity of a solution. The pH scale is a measure of the hydrogen ion (H+) concentration. The pH scale is a measure of the hydrogen ion (H+) concentration. pH actually measures the hydronium ion concentration ([H 3 O +1 ]) of a solution. pH actually measures the hydronium ion concentration ([H 3 O +1 ]) of a solution. We use acid-base indicators to measure the pH of a solution. We use acid-base indicators to measure the pH of a solution. Scale runs from 0 to 14. Scale runs from 0 to 14. Bases have pH>7; [H 3 O +1 ] 7; [H 3 O +1 ]<1 x M Acids have pH 1 x M Acids have pH 1 x M Neutral solns:pH=7; [H 3 O +1 ]=1 x10 -7 M Neutral solns:pH=7; [H 3 O +1 ]=1 x10 -7 M > > > > 14

pH

The pH Scale: Some Examples pH ValueH + Concentration Relative to Pure Water Example battery acid sulfuric acid lemon juice, vinegar orange juice, soda tomato juice, acid rain 5100black coffee, bananas 610urine, milk 71pure water 80.1sea water, eggs 90.01baking soda Great Salt Lake, milk of magnesia ammonia solution soapy water bleach, oven cleaner liquid drain cleaner

Self ionization of water: H 2 O + H 2 O  H 3 O + + OH - H 2 O + H 2 O  H 3 O + + OH - Hydronium ion: H 3 O + Hydronium ion: H 3 O + Hydroxide ion: OH - Hydroxide ion: OH - Only 1 x 10 –14 M of water molecules do this so Only 1 x 10 –14 M of water molecules do this so [H 3 O + ][OH - ] = 1 x 10 –14 M [H 3 O + ][OH - ] = 1 x 10 –14 M If [H 3 O + ]=[OH - ] neutral solution If [H 3 O + ]=[OH - ] neutral solution If [H 3 O + ]>[OH - ] acidic solution If [H 3 O + ]>[OH - ] acidic solution If [H 3 O + ]<[OH - ] basic or alkaline solution If [H 3 O + ]<[OH - ] basic or alkaline solution

Formulas: we can calculate the pH of a solution if we know [H 3 O +1 ]: ( recall: H 3 O +1 same as H +1 ) pH=-log [H 3 O +1 ] or =-log [H +1 ] pH=-log [H 3 O +1 ] or =-log [H +1 ] Use to find pH given [H + ] Use to find pH given [H + ] 1. Find the pH if the hydronium ion concentration is 2.1 X M. Is this solution of baking soda acidic or basic? 1. Find the pH if the hydronium ion concentration is 2.1 X M. Is this solution of baking soda acidic or basic? (on calculator enter 2.1, EE, -5, log, +/-) (on calculator enter 2.1, EE, -5, log, +/-) 2. What is the pH of a solution of baking soda which has an [H 3 O +1 ] of 3.98 x M? 2. What is the pH of a solution of baking soda which has an [H 3 O +1 ] of 3.98 x M? Is this solution of baking soda acidic or basic? Is this solution of baking soda acidic or basic? 3. Find the pH of a M HCl solution. The HCl is a strong acid and is 100% ionized in water. The hydronium ion concentration is M. 3. Find the pH of a M HCl solution. The HCl is a strong acid and is 100% ionized in water. The hydronium ion concentration is M. HCl › H+ + Cl- HCl › H+ + Cl M M M M

Formulas: we can calculate the pOH of a solution if we know [OH -1 ]: pOH= -log [OH - ] pOH= -log [OH - ] Use to find pOH given [OH - ] Use to find pOH given [OH - ] 1.Find the pOH if the hydroxide ion concentration is 4.1 X M. (on calculator enter 4.1, EE, -5, log, +/-) (on calculator enter 4.1, EE, -5, log, +/-) 2. What is the pOH of a solution that has a hydroxide ion concentration of 4.82 x M?

Formulas we can also calculate the hydronium ion concentration ([H3O +1 ]) if we know the hydroxide ion concentration ([OH -1 ]) or vice versa [H 3 O + ][OH - ]= 1 X 10 –14 M or [H + ][OH - ]= 1 X 10 –14 M Use to find one [ ] given the other [ ] Use to find one [ ] given the other [ ] 1. What is the [H3O +1 ] of a solution if the [OH -1 ] is equal to 1 x M ? [H3O +1 ] x [OH -1 ] = 1 x [H3O +1 ] x [OH -1 ] = 1 x [H3O +1 ] x [1 x M] = 1 x [H3O +1 ] x [1 x M] = 1 x [H3O +1 ] = [1 x ] =1 x M [H3O +1 ] = [1 x ] =1 x M [1 x M] [1 x M] 2.Find the [OH - ] ion concentration if the hydronium ion concentration is 1 x M. Is this acidic, basic or neutral? 2.Find the [OH - ] ion concentration if the hydronium ion concentration is 1 x M. Is this acidic, basic or neutral? 3. If the hydroxide concentration is 3. If the hydroxide concentration is 1 x 10 –4 M, what is the hydronium ion 1 x 10 –4 M, what is the hydronium ion concentration? concentration?

pH pH: pH: Acid neutral base Acid neutral base pOH: pOH: Each one unit change in the pH represents a ten-fold change in the [H3O+]. If you increase the acid or base strength by a concentration factor of 10, the pH will change by 1. Each one unit change in the pH represents a ten-fold change in the [H3O+]. If you increase the acid or base strength by a concentration factor of 10, the pH will change by 1. As the H3O+ concentration increases, the pH will decrease (becomes more acidic and less basic). As the H3O+ concentration increases, the pH will decrease (becomes more acidic and less basic). If H3O+ is 1.0 x 10-7 and is changed to 1.0 x 10-5 (by the addition of more acid). Then the concentration of H3O+ has increased so the pH goes from 7 to 5 (decreases). If H3O+ is 1.0 x 10-7 and is changed to 1.0 x 10-5 (by the addition of more acid). Then the concentration of H3O+ has increased so the pH goes from 7 to 5 (decreases). As the H3O+ ion concentration decreases, the pH will increase (becomes more basic and less acidic).The pH value represents the relationship between the H3O+ concentration and the OH- concentration. As the H3O+ ion concentration decreases, the pH will increase (becomes more basic and less acidic).The pH value represents the relationship between the H3O+ concentration and the OH- concentration. [H3O+] + [OH-] = 1 x [H3O+] + [OH-] = 1 x Since the pH tells you the concentration of the H3O+, then you can use the pH to calculate the concentration of OH- in a solution. Since the pH tells you the concentration of the H3O+, then you can use the pH to calculate the concentration of OH- in a solution.

pH/ pOH pH + pOH = 14 pH + pOH = 14 Use to find one given the other. Use to find one given the other. 1. Find the pOH if the pH is Find the pOH if the pH is 8.2. pOH= = 5.8 pOH= = 5.8 [H + ]= 10 -pH or [H+] = antilog (- pH) [H + ]= 10 -pH or [H+] = antilog (- pH) Use to find [H + ] given to pH Use to find [H + ] given to pH 2. Find the [H + ] given a pH of Find the [H + ] given a pH of [on calculator enter 11.5, +/-, 2nd, log (10x)] [on calculator enter 11.5, +/-, 2nd, log (10x)] 3. Calculate the [H+] for a solution with a pH of Calculate the [H+] for a solution with a pH of [OH - ]= 10 -pOH or antilog (- pOH) [OH - ]= 10 -pOH or antilog (- pOH) Use to find [OH - ] given to pOH Use to find [OH - ] given to pOH 4. Find the [OH - ] given a pOH of Find the [OH - ] given a pOH of 7.5 [on calculator enter 7.5, +/-, 2nd, log (10x)] [on calculator enter 7.5, +/-, 2nd, log (10x)] What is the pH? What is the pH? Is the solution acidic, basic or neutral? Is the solution acidic, basic or neutral? 5. What is the hydroxide ion concentration in a solution that has a pOH of 5.70? 5. What is the hydroxide ion concentration in a solution that has a pOH of 5.70? What is the pH? What is the pH? Is the solution acidic, basic or neutral? Is the solution acidic, basic or neutral?