ACIDS, BASES AND SALTS A guide for A level students 2015 SPECIFICATIONS KNOCKHARDY PUBLISHING

ACIDS, BASESACIDS, BASESAND SALTSAND SALTSA guide for A level studentsA guide for A level students

20152015 SPECIFICATIONSSPECIFICATIONSKNOCKHARDY PUBLISHINGKNOCKHARDY PUBLISHING

INTRODUCTION

This Powerpoint show is one of several produced to help students understand selected topics at AS and A2 level Chemistry. It is based on the requirements of the AQA and OCR specifications but is suitable for other examination boards.

Individual students may use the material at home for revision purposes or it may be used for classroom teaching if an interactive white board is available.

Accompanying notes on this, and the full range of AS and A2 topics, are available from the KNOCKHARDY SCIENCE WEBSITE at...

www.knockhardy.org.uk/sci.htm

Navigation is achieved by...

either clicking on the grey arrows at the foot of each page

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ACIDS, BASES AND SALTSACIDS, BASES AND SALTS

BRØNSTED-LOWRY THEORY

ACID proton donor HCl ——> H+(aq) + Cl¯(aq)

BASE proton acceptor NH3(aq) + H+(aq) ——> NH4+(aq)

ACIDS AND BASESACIDS AND BASES

ACIDS proton donors release H+ ions (protons) in aqueous solution

STRONG ACIDS

Hydrochloric HCl —> H+(aq) + Cl¯(aq) 1 replaceable H MONOPROTIC

Nitric HNO3 —> H+(aq) + NO3¯(aq) 1 replaceable H MONOPROTIC

Sulphuric H2SO4 —> 2H+(aq) + SO42-(aq) 2 replaceable H’s DIPROTIC

ACIDSACIDS

ACIDS proton donors release H+ ions (protons) in aqueous solution

STRONG ACIDS

Hydrochloric HCl —> H+(aq) + Cl¯(aq) 1 replaceable H MONOPROTIC

Nitric HNO3 —> H+(aq) + NO3¯(aq) 1 replaceable H MONOPROTIC

Sulphuric H2SO4 —> 2H+(aq) + SO42-(aq) 2 replaceable H’s DIPROTIC

WEAK ACIDS

Ethanoic CH3COOH(aq) CH3COO¯(aq) + H+(aq) MONOPROTIC

ACIDSACIDS

BASES proton acceptors react with acids by accepting H+ ions to form salts

e.g. carbonates K2CO3 MgCO3 CuCO3

hydrogencarbonates NaHCO3

metal oxides MgO ZnO CuOmetal hydroxides NaOH KOH Ca(OH)2

ammonia NH3

BASES AND ALKALISBASES AND ALKALIS

BASES proton acceptors react with acids by accepting H+ ions to form salts

e.g. carbonates K2CO3 MgCO3 CuCO3

hydrogencarbonates NaHCO3

metal oxides MgO ZnO CuOmetal hydroxides NaOH KOH Ca(OH)2

ammonia NH3

ALKALIS SOLUBLE BASES which release OH¯ (hydroxide ions) in aqueous solution

e..g. Soluble metal oxidessodium oxide Na2O + H2O(l) ——> 2Na+(aq) + 2OH¯(aq)

Soluble metal hydroxidessodium hydroxide NaOH ——> Na+(aq) + OH¯(aq)

potassium hydroxide KOH ——> K+(aq) + OH¯(aq)

Aqueous ammonia NH3(aq) + H2O(l) NH4+ (aq) + OH¯(aq)

or NH3(aq) + H+(aq) NH4+(aq)

BASES AND ALKALISBASES AND ALKALIS

SALTS Formed from the reaction between acids and baseshydrochloric acid makes CHLORIDESnitric acid makes NITRATESsulphuric acid makes SULPHATES / HYDROGENSULPHATES

SALTFORMATION A salt is produced when the H+ ion of an acid is replaced by...

a metal ion or the ammonium ion NH4

+

SALTSSALTS

SALTS Formed from the reaction between acids and baseshydrochloric acid makes CHLORIDESnitric acid makes NITRATESsulphuric acid makes SULPHATES / HYDROGENSULPHATES

SALTFORMATION A salt is produced when the H+ ion of an acid is replaced by...

a metal ion or the ammonium ion NH4

+

SUMMARYAcids react with...

metals to give a salt + hydrogenoxides of metals a salt + waterhydroxides of metals a salt + watercarbonates a salt + water + carbon dioxidehydrogencarbonates a salt + water + carbon dioxideammonia an ammonium salt

SALTSSALTS

Water ofcrystallisation • loosely bonded water molecules attached to salts

CuSO4.5H2OFeSO4.7H2ONa2CO3.10H2O

• the water can be driven off by heating

e.g. CuSO4.5H2O(s) ———> CuSO4(s) + 5H2O(l)

WATER OF CRYSTALLISATIONWATER OF CRYSTALLISATION

Water ofcrystallisation • loosely bonded water molecules attached to salts

CuSO4.5H2OFeSO4.7H2ONa2CO3.10H2O

• the water can be driven off by heating

e.g. CuSO4.5H2O(s) ———> CuSO4(s) + 5H2O(l)

HYDRATED copper(II) sulphate ANHYDROUS copper(II) sulphateBLUE CRYSTALS WHITE POWDER

WATER OF CRYSTALLISATIONWATER OF CRYSTALLISATION

Is a typical acid in dilute aqueous solution HCl ——> H+ (aq) + Cl¯(aq)

REACTIONS OF HYDROCHLORIC ACID REACTIONS OF HYDROCHLORIC ACID

Hydrogen chloride is a colourless covalent gas; it is a poor conductor of electricity because there are no free electrons or ions present. It has no action on dry litmus paper because there are no aqueous hydrogen ions present.




If the gas is passed into water, the hydrogen chloride molecules dissociate into ions. The solution now conducts electricity showing ions are present. For each hydrogen chloride molecule that dissociates one hydrogen ion and one chloride ion are produced. The solution turns litmus paper red because of the H+(aq) ions.







HYDROGEN CHLORIDE HYDROCHLORIC ACID

colourless gas Appearance colourless soln.covalent molecule Bonding aqueous ionsHCl(g) Formula HCl(aq) poor Conductivity goodno reaction Dry blue litmus goes red



Appearance Bonding and formula Conductivity Dry litmushydrogen chloride colourless gas covalent molecule HCl(g) poor no reactionhydrochloric acid colourless soln. aqueous ions HCl(aq) good goes red



SUMMARY

Metals magnesium + dil. hydrochloric acid ——> magnesium chloride + hydrogen

Mg(s) + 2HCl(aq) ——> MgCl2(aq) + H2(g)


1. WRITE OUT THE BALANCED EQUATION FOR THE REACTION



Mg(s) + 2H+(aq) + 2Cl¯(aq) ——> Mg2+(aq) + 2Cl¯(aq) + H2(g)


1. WRITE OUT THE BALANCED EQUATION FOR THE REACTION2. DILUTE ACIDS AND SALTS CONTAIN IONS; WATER, HYDROGEN & CARBON DIOXIDE DON’T




cancel ions Mg(s) + 2H+(aq) ——> Mg2+(aq) + H2(g)


1. WRITE OUT THE BALANCED EQUATION FOR THE REACTION2. DILUTE ACIDS AND SALTS CONTAIN IONS; WATER, HYDROGEN & CARBON DIOXIDE DON’T3. CANCEL OUT THE IONS WHICH APPEAR ON BOTH SIDES OF THE EQUATION




cancel ions Mg(s) + 2H+(aq) ——> Mg2+(aq) + H2(g)

BasicOxides copper(II) oxide + dil. hydrochloric acid ——> copper(II) chloride + water

CuO(s) + 2HCl(aq) ——> CuCl2(aq) + H2O(l)

Cu2+O2-(s) + 2H+(aq) + 2Cl¯(aq) ——> Cu 2+ (aq) + 2Cl¯(aq) + H2O(l)

cancel ions O2- + 2H+(aq) ——> H2O(l)


Alkalis sodium hydroxide + dil. hydrochloric acid ——> sodium chloride + water

NaOH(aq) + HCl(aq) ——> NaCl(aq) + H2O(l)

Na+(aq) + OH¯(aq) + H+(aq) + Cl¯(aq) ——> Na+ (aq) + Cl¯(aq) + H2O(l)

cancel ions H+(aq) + OH¯(aq) ——> H2O(l)






Carbonates calcium carbonate + hydrochloric acid ——> calcium chloride + carbon dioxide + water

CaCO3(s) + 2HCl(aq) ——> CaCl2(aq) + CO2(g) + H2O(l)

Ca2+CO32-(s) + 2H+(aq) + 2Cl¯(aq) ——> Ca2+(aq) + 2Cl¯(aq) + CO2(g) + H2O(l)

cancel ions CO32- + 2H+(aq) ——> CO2(g) + H2O(l)






Carbonates calcium carbonate + hydrochloric acid ——> calcium chloride + carbon dioxide + water

CaCO3(s) + 2HCl(aq) ——> CaCl2(aq) + CO2(g) + H2O(l)

Ca2+CO32-(s) + 2H+(aq) + 2Cl¯(aq) ——> Ca2+(aq) + 2Cl¯(aq) + CO2(g) + H2O(l)

cancel ions CO32- + 2H+(aq) ——> CO2(g) + H2O(l)

Hydrogen carbonates H+(aq) + HCO3¯ ——> CO2(g) + H2O(l)


SUMMARY

METALS react to give a salt + hydrogen

METAL OXIDES react to give a salt + water

METAL HYDROXIDES react to give a salt + water

CARBONATES react to give a salt + water + carbon dioxide

HYDROGENCARBONATES react to give a salt + water + carbon dioxide

AMMONIA reacts to give an ammonium salt


© 2015 JONATHAN HOPTON & KNOCKHARDY PUBLISHING© 2015 JONATHAN HOPTON & KNOCKHARDY PUBLISHING

THE ENDTHE END

ACIDS, BASESACIDS, BASESAND SALTSAND SALTS

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ACIDS, BASES AND SALTS A guide for A level students 2015 SPECIFICATIONS KNOCKHARDY PUBLISHING