Comments:

Aleen

Her answers are well-written and reader-friendly. She provides accurate and informative answers. However, for question 4ii) and 5i), the question is asking for the ionic equations, but both her answers are in chemical equations.

Yihui

Her answers are short and straightfoward. For question 1, zinc hydroxide , ZnOH should be Zn(OH)2. For question 5, it would be better in she includes "add until there is excess solid" so that it's able to filtrate.

ChunBoon

His answers are excellent. I would prefer him putting Zn2+ instead of Zn(+). To make his life more easier, he can write on a piece of paper and post it. And also, he made a slight mistake in question 1 iv), it should be Zn2+ instead of Zn(+). For question 3iii), it is supposed to be Iron (II) ion instead of Iron (III) ion which gives the green soluion.

Overall, everyone's answers are great. I can see them putting in effort in providing quality answers ^o^

Question 5: Excess zinc carbonate is added to hydrochloric acid in the preparation of zinc chloride salt.

(i) Write an ionic equation for the reaction.

(ii) Why excess zinc carbonate is used?

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

(i)

(ii) To ensure that zinc carbonate is completely reacted with hydrochloric acid.

(iii) By adding zinc carbonate to the hydrochloric acid until there's excess solid left. Filter to remove excess unreacted zinc carbonate. Heat the filtrate until it's left with some water for crystallisation.

Question 4: 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.

(ii) Write an ionic equation for the reaction.

(i) Potassium sulfate is a Group I salt, which is soluble. Since both solutions are colourless, we can used titration method and an indicator to determine the end-point of neutralisation between the two solutions.

(ii)

Question 3: 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.

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

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

(i) Ammonia gas

(ii) Nitrates

(iii) Iron (II) ion

Question 2: Ammonium sulfate is heated with sodium hydroxide.

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

(ii) Describe a test for the gas.

Question 1: Zinc nitrate reacts with aqueous ammonia (NH4OH) to form a salt and a base.

(i) Name the salt and the base.

(ii) Describe the observations for the reaction.

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