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12.8Chapter 12: Chemical Reactions 3 and Rates

Making salts from acids and carbonates — Alhussan Chemistry - Stage 9 Revision Notes & Topical Questions

5 min read 8 parts Lesson 8 of 13 2 quizzes

📚 Alhussan Chemistry - Stage 9 Hub / Topical Revision
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Lesson summary

12.8 Making salts from acids and carbonates — Alhussan International Academy — Chemistry (Stages 7–9) notes: Describe how to make a salt from an acid and an insoluble carbonate, identify the gas produced and evaluate and improve the method.General equation — metal carbonate + aci…

  • Symbol equations
  • Positive result
  • Other gases
  • Fungicides
  • Reaction 1
  • Reaction 2

Part 1 of 6The reaction

General equation
  • General equation metal carbonate + acid → salt + water + carbon dioxide.
  • calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide.
  • copper carbonate + sulfuric acid → copper sulfate + water + carbon dioxide.
Symbol equations
  • CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g) and CuCO3(s) + H2SO4(aq) → CuSO4(aq) + H2O(l) + CO2(g).
Fizzing
  • Fizzing it shows carbon dioxide is released and how the reaction is progressing.

Part 2 of 6Test for carbon dioxide

Test
  • Test bubble the gas through limewater.
    • (calcium hydroxide solution)
Positive result
  • Positive result the limewater goes cloudy or milky because of tiny particles of insoluble calcium carbonate.
Other gases
  • Other gases do not confuse it with hydrogen (squeaky pop) or oxygen.
    • (relights a glowing splint)

Part 3 of 6Choosing the method to make copper sulfate

Fungicides
  • Fungicides copper sulfate is used by some farmers as a fungicide to destroy fungi that damage crops.
Reaction 1
  • Reaction 1 copper + sulfuric acid → copper sulfate + hydrogen, which needs concentrated acid and a high temperature.
Reaction 2
  • Reaction 2 copper oxide + sulfuric acid → copper sulfate + water, which can use dilute acid.
Reaction 3
  • Reaction 3 copper carbonate + sulfuric acid → copper sulfate + carbon dioxide + water, which can use dilute acid.
Industry and school
  • Industry and school industry uses reactions 1 and 2, while school uses reaction 2 or 3 because reaction 1 is too hazardous.

Part 4 of 6Method to make a salt from a carbonate

1
Measure 25 cm3 of dilute acid and pour it into a beaker, after doing a risk assessment.
2
Add the carbonate powder one spatula at a time, stirring, so carbon dioxide forms and the mixture bubbles.
3
Stop when some carbonate remains and there is no more bubbling, which shows all the acid has reacted.
4
Filter the mixture so the unreacted carbonate stays in the filter paper and the salt solution is collected.
5
Heat the solution in an evaporating basin until blue crystals start to form around the edge.
6
Let it cool in a warm, dry place so the water evaporates slowly and crystals form, then filter, wash and dry them.
1Stages
  • Stages reaction, filtration, evaporation and crystallisation.
2Evaporating basin
  • Evaporating basin collecting the filtrate straight into it means the solution does not need pouring from one container to another.
3Safety of carbonates
  • Safety of carbonates they are safer than reactive metals, and add small portions so the mixture does not froth over.
4Soluble carbonates
  • Soluble carbonates with sodium carbonate an indicator or titration is needed to find the neutral point.

Part 5 of 6Evaluating and improving the method

Problem
  • Dan made a smaller mass of crystals than expected because some solution spat out during evaporation.
Improvement
  • Improvement heating over a water bath rather than a flame heats the solution more evenly and prevents spitting.
  • The second attempt gave a greater mass of crystals.
Rates experiment
  • Rates experiment the volume of gas produced in a fixed time, or the time for fizzing to stop, can compare powdered and lump carbonate.
  • 5.0 g of calcium carbonate reacting with excess acid loses 2.2 g in mass, which is the mass of carbon dioxide released.

Part 6 of 6Everyday links

Limestone and marble
  • Limestone and marble buildings and statues are carbonates, and acid rain makes the stone fizz slowly and wear away.
Indigestion tablets
  • Indigestion tablets they contain carbonates that neutralise excess stomach acid.
Soil
  • Soil calcium carbonate is added to soil to reduce acidity.
Identifying carbonates
  • Identifying carbonates add dilute acid to an unknown solid and test any gas with limewater.
Reaction typeProducts
Acid + metalSalt + hydrogen
Acid + oxideSalt + water
Acid + carbonateSalt + water + carbon dioxide

Key terms

TermMeaning
Carbonatea compound containing the CO3 group.
Limewatera solution used to test for carbon dioxide.
Effervescencefizzing caused by gas bubbles.
Neutraliseto react an acid fully with a base.
Fungicidea chemical that destroys fungi.
Water batha beaker of hot water used for gentle, even heating.

Avoid these mistakes

1
Writing hydrogen as a product — a carbonate gives carbon dioxide.
2
Forgetting water as a product — water forms as well as the salt and carbon dioxide.
3
Using a lit splint for carbon dioxide — use limewater.
4
Adding all the carbonate at once — it can froth over.

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