comments on friends!!

On Shuyu(12)- I think she put in a lot effort doing it! Her answers are very clear and easy to understand, she even take the effort to make a range of colours for the questions and answers which make it even neater and easy to read. But i think it would be better if she show the working of how she obtain the ionic equations

On Cindy(02)- great effort as well!! I like her way of answering the question it make me understand more. It is really a good idea to write the ionic equation on the paper and scan into the computer, i actually learn from her XD her picture are very clear and neat, she show the working too which is very good. Her answer is very detail as well like for q1(ii) she mention that "a colourless soluble salt ammonium nitrate", very few people mention about this point which i think is very important too.

On Jieen(13)- She put in effort doing it too! nice answer!! Her answers are clear-cut and easy to understand. Like what i mentioned earlier i think it would be better if she show the working of how she obtain the ionic equations. For q4(i) many people only write one sentence and give a brief explaination but her answer is very detail and useful!

To conclude, i think all three of them really spend time and effort doing it, i couldn't manage to find only mistake so very well done!!! :)

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 Zn(OH)2 . The base is Ammonium Nitrate NH4NO3.

(ii) Describe the observations for the reaction.
A white precipitate of zinc hydroxide Zn(OH)2 is formed.

(iii) Write a chemical equation for the reaction.
Zn(NO)3(aq) + 2NH4OH(aq) --> Zn(OH)2(s) + 2NH4NO3(aq)

(iv) Write an ionic equation for the reaction.

Q2 Ammonium sulfate is heated with sodium hydroxide.

(i)Write a chemical equation for the reaction.

(NH4)2SO4 (aq) + 2NaOH (aq) -> Na2SO4 (s) + 2NH3 (g) + 2H2O (l)

(ii) Describe a test for the gas.

Ammonia gas will turn red damp litmus paper to blue in colour.

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 gas

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

The anion is Nitrate (NO3-)

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

The possible cation is Iron(III) Fe2+.

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.

Potassium sulfate is a group (I) salt and is soluble.

(ii) Write an ionic equation for the reaction.

Q5 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?

It is used to ensure that all the hydrochloric acid is completely reacted with the zinc carbonate.

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

Step 1: Add excess zinc carbonate solid to beaker of dilute hydrochloric acid until there is excess white zinc carbonate solid left behind.

Step 2: filter to remove the excess unreacted zinc carbonate solid.

Step 3: evaporate the zinc chloride solution to remove water and make a saturated salt solution.

Step 4: the hot saturated solution form zinc chloride salt when it is cooled.