フィクション

Q1 Zinc nitrate reacts with aqueous ammonia (NH4OH) to form a salt and a base.

(i) Name the salt and the base.

The salt is Zinc Hydroxide. The base is Ammonium Nitrate .

ii) Describe the observations for the reaction.

When Zinc Nitrate and aqueous ammonia react with one another, a white precipitate will be formed.

(iii) Write a chemical equation for the reaction (include state symbols).

ZnNO3(aq) + 2NH4OH (aq) > Zn(OH)2 (s) + 2NH4NO3 (aq)

(iv) Write an ionic equation for the reaction.

Zn 2+ (aq) + OH- (aq) > Zn(OH)2 (s)

Q2 Ammonium sulfate is heated with sodium hydroxide.

(i) Write a chemical equation (include state symbols) for the reaction.

(NH4)2 SO4 (aq) + 2NaOH > Na2 SO4 (aq) + 2H2O (i) +2 NH3 (g)

(ii) Describe a test for the gas.

It turns damp red litmus paper blue.

Q3 An unknown green solution is heated with a piece of aluminium foil and sodium hydroxide solution.

(i) The gas produced turns damp red litmus paper blue. Name the gas evolved.

Ammonia

(ii) This is a confirmatory test for an anion. Name this anion.

Nitrate

(iii) Give a possible cation which gives the green solution.

Iron (II)

Q4 Sulfuric acid is titrated with potassium hydroxide in the preparation of potassium sulfate salt.

(i) Explain why this method is recommended for the preparation for this salt.

It is soluble Group I salt and hence by using titration method, we will be able to get the salt.

(ii) Write an ionic equation for the reaction.

H+ (aq) + OH- (aq) > H2O (L)

Q5 Excess zinc carbonate is added to hydrochloric acid in the preparation of zinc chloride salt.

(i) Write an ionic equation for the reaction.

ZnCO3 (s) + H+ (aq) > Zn+ (aq) + H2O(L) + CO2(g)

(ii) Why excess zinc carbonate is used?

It is used to ensure that zinc carbonate and hydrochloric acid is fully reacted.

(iii) Briefly explain how the zinc chloride crystals can be obtained.

As there is excess black zinc carbonate solid left , filter to remove the excess unreacted and evaporate it to form a saturated salt solution. The hot saturated solution will then form zinc chloride crystals when it is being cooled down.