Sunday, March 6, 2011

2P05 Answers Courtesy of Chen Dewei (Group 4)

OBSERVATIONS
When calcium carbonate is added to hydrochloric acid:
Effervescence is observed. NO white precipitate is formed.
Effect of gas on limewater:
White precipitate is observed
Effect of gas on damp litmus paper:
The gas turns blue litmus paper red, while for the red litmus paper, there is no observable change.


1. When a dilute acid and a carbonate react, a salt, carbon dioxide and water are produced.
2. Dilute acid + carbonate -> salt + carbon dioxide + water
3. 
1. A white precipitate is formed.
2. The reaction is more vigorous.
3. Different salts are formed (calcium chloride and calcium sulfate)
 EXPLANATION
 Calcium chloride is soluble in acid while calcium sulfate is insoluble in acid. Different salts are formed. H2SO4    has 2 hydrogen atoms, while HCl has only 1 hydrogen atom, thus there's more acidity and therefore the reaction will be more vigorous.
4. Place a tube to transport the gas to a test-tube of limewater. If a white precipitate is formed, the gas is carbon dioxide.
5 (a) acidic
   (b) Bubble the sample of air through limewater (calcium hydroxide). Since limewater is a base, carbon dioxide (an acidic gas) will react with it.
Calcium carbonate + Hydrochloric acid à calcium chloride + carbon dioxide + water
CaCO3 + 2HCl -> CaCl2 + CO2 + H2O
Sodium carbonate + hydrochloric acid à sodium chloride + carbon dioxide + water
Na2CO3 + 2HCl -> 2NaCl + CO2 + H2O
Potassium carbonate + hydrochloric acid à potassium chloride + carbon dioxide +water
K2CO3 + 2HCl -> 2KCl + CO2 + H2O
Calcium carbonate + nitric acid à calcium nitrate + carbon dioxide + water
CaCO3 + 2HNO3 -> Ca(NO3)2 + CO2 + H2O
Sodium carbonate + nitric acid à sodium nitrate + carbon dioxide + water
Na2CO3 + 2HNO3 -> 2NaNO3 + CO2 + H2O
Potassium carbonate + nitric acid à potassium nitrate + carbon dioxide + water
K2CO3 + 2HNO3 -> 2KNO3 + CO2 + H2O
Calcium carbonate + sulfuric acid à calcium sulfate + carbon dioxide + water
CaCO3 + H2SO4 -> CaSO4 + CO2 + H2O
Sodium carbonate + sulfuric acid à sodium sulfate + carbon dioxide + water
Na2CO3 + H2SO4 -> Na2SO4 + CO2 + H2O
Potassium carbonate + sulfuric acid à potassium sulfate + carbon dioxide + water
K2CO3 + H2SO4 -> K2SO4 + CO2 + H2O
Sodium carbonate + ethanoic acid à  sodium ethanoate + carbon dioxide + water
Na2CO3 + 2CH3COOH -> 2Ch3COONa + CO2 + H2O
Potassium carbonate + ethanoic acid à potassium ethanoate + carbon dioxide + water
K2CO3 + 2CH3COOH -> 2CH3COOK + CO2 + H2O
Calcium carbonate + ethanoic acid à calcium ethanoate + carbon dioxide + water
CaCO3 + 2CH3COOH -> (CH3COO)2Ca + CO2 + H2O

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