2 What do all these acids have in common: Strong AcidsThe FormulaSulphuric acidHydrochloric acidHydrobromic acidHydroiodic acidNitric acidPerchloric acidH2SO4HClHBrHIHNO3HClO4Weak Acid The FormulaAcetic acid (vinegar) HC2H3O2Carbonic acid HCO3
3 Acid:A substance that ionises (breaks down into ions) and releases H+ ions in an aqueous solution“aqueous” means: water
4 Characteristics of Acids: Acids have a sour tasteAcids react with metals (to produce hydrogen gas)Acids have a pH of 1-6Acids turn universal indicator yellow, orange or redAcids turn litmus redMany are corrosive or poisonous
5 You need to know three acids Sulfuric acidH2SO4hydrochloric acidHClNitric acidHNO3
6 All are Strong AcidsIonise (break down into ions) completely to give off many H+ ions
8 Weak Acids(only partially breaks down (ionise), gives less H+)
9 What do these bases have in common: Strong BasesThe FormulaeLithium hydroxideSodium hydroxidePotassium hydroxideRubidium hydroxideCaesium hydroxideBarium hydroxideCalcium hydroxideStrontium hydroxideLiOHNaOHKOHRbOHCsOHBa(OH)2Ca(OH)2Sr(OH)2
10 Base:A substance that ionises and releases OH- ions in an aqueous solutionAlkali:A base that dissolves in water
11 OH- Characteristics of Bases: Bases usually taste bitter Bases feel slipperyBases have a pH of 8 – 14Bases turn universal indicator blue or purpleBases turn litmus blueOH-
12 BUT AREN’T METAL OXIDES BASES? Yes!!!!!!Metal oxide + water metal hydroxideMetal oxides release hydroxide ions in solution
13 Some bases (VERY FEW)don’t have or produce OH-Examples include:ammonia NH3Carbonates (CO3 and HCO3)***Any chemical which neutralizes an acid can be considered a base
14 IndicatorsAn indicator is a compound that will change color in the presence of an acid or baseRed Litmus-Turns blue in baseBlue Litmus-Turns red in acidUniversal indicator (pH paper) Used for the full pH rangePhenolphthalein-Turns pink in base
15 pHpH stands for “potential of Hydrogen” and is a measure of how many H+ ions there are in solution.The MORE H+ there are, the LOWER the pH will be.
16 Shows the range of H+ concentrations pH ScaleShows the range of H+ concentrationsHigh H+ concentrationLow H+ concentration
17 Reactions between acids and bases When an acid and a base react with each other , the characteristic properties of both are destroyed. This is called neutralisation.This happens because equal amounts of the two substances cancel each others properties and produce two neutral substances (water and a salt).
18 Reactions between acids and bases General formula for acid base reaction:→++BaseWaterSaltAcid“Salt” means any ionic compound formed from an acid/base reactionNOT JUSTNaCl !!
19 NeutralisationHCl + NaOH → H2O + NaClacid base water salt
20 Neutralisation H Cl K OH Another Example HCl + KOH → H2O + KCl acid base water salt
21 Complete and incomplete neutralisation Any time an acid and base react neutralisation will occur. However, whether the solutions are fully neutralised depends on several factors:The pH of both reactantsThe concentration of both reactantsThe quantity of both reactantsIf any of these factors occur then neutralisation will be incomplete. This means in the solution there will be a metal salt, water and an acid or base.
22 Name the following compounds CaONaOHNa2SPbCO3CuHCO3Ag2OPbCl2CuSO4
23 General equationsThese are all extensions of the acid + base equationsAcid + metal oxide metal salt + waterAcid + metal hydroxide Metal salt + waterAcid + Metal carbonate metal salt+ water + carbon dioxideAcid + metal hydrogen carbonate metal salt + water+ carbon dioxide
24 WHAT SALT IS FORMED DEPENDS ON WHAT ACID IS USED Hydrochloric acid makes a chloride saltSulfuric acid makes a sulfate saltNitric acid makes a nitrate salt
25 Predict what acid these salts were made from NaNO3CaSO4PbCl2CuCl2Fe2(SO4)3Fe(NO3)2
26 Complete the following as word equations only Hydrochloric acid + Calcium hydroxideSulphuric acid + Lead oxideNitric acid + sodium bi-carbonateSilver oxide + sulphuric acidCopper carbonate + nitric acid
28 NCEA 2009A student carried out an experiment to neutralise sulfuric acid by adding sodium hydroxide to it.Discuss how the student could have determined when the sulfuric acid had been neutralised and what effect adding the sodium hydroxide has on the pH of the solution.In your answer include:• an explanation of neutralisation in terms of an acid-base reaction• the name of the indicator used• observations that the student would make as the sodium hydroxide is added to the acid• a word and balanced chemical equation for the reaction.
30 NCEA 2006 The pH values of three substances are given below: Hydrochloric acid pH = 1Potassium carbonate solution pH = 9Sodium hydroxide solution pH = 14(a) When Universal Indicator solution is added to each of these substances, what colour would result?(i) Hydrochloric acid __________________(ii) Potassium carbonate solution __________________(iii) Sodium hydroxide solution __________________Potassium carbonate solution is added slowly to the hydrochloric acid (without indicator) in a beaker until no further change is seen.(b) (i) Describe what you would see happening when potassium carbonate is added to the acid.(ii) Write a balanced chemical equation for the reaction between potassium carbonate and hydrochloric acid.