#5

EXCESS ZINC CARBONATE IS ADDED TO HYDROCHLORIC ACID IN THE PREPARRATION OF ZINC CHLORIDE SALT. 

(i) Write an ionic equation for this reaction


ZnCO3 (aq) + 2HCl (aq) à  ZnCl (aq) + H2O (l) + CO2 (g)








(ii) Why is excess Zinc Carbonate used? 


This is to ensure that ALL Zinc Carbonate has completely neutralized with the acid before we filter out the excess unreacted solid from the salt solution.








(iii) Briefly explain how the Zinc Chloride Crystals can be obtained


Excess ZnCO3 will be added to HCl until a black, insoluble unreacted solid can be seen. Filtration is carried out to remove the excess unreacted solid. The solution of reacted and neutralized solution then undergoes evaporation to remove the water and make a saturated salt solution. The hot saturated solution is left to cool to obtain the zinc chloride crystals.

#4

SULFURIC ACID IS TITRATED WITH POTASSIUM HYDROXIDE IN PREPARATION OF POTASSIUM SULFATE SALT

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

Pottasium Sulfate is a Group (I) salt and it is soluble. The solutions used are all also colourless, and because of this we would need an indicator (provided in titration method) to indicate the end point of neutrolization between the acid and alkali before preparing the salt.

(ii) Write an ionic equation for the reaction

H2SO4 (aq) + 2KOH (aq) à K2SO4 (aq) + 2H2O (l)

#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.

Ammonia gas

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

Nitrates.

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

Iron(II) ions (Fe 2+)

#2

AMMONIUM SULFATE IS HEATED WITH SODIUM HYDROXIDE

(i) Write the chemical equation (including state symbols) for the reaction


 (NH4)2SO4 (aq) + 2NaOH (aq) à   NA2SO4 (aq)+ 2H2O (l) + 2NH3 (g)

(ii) Describe a test for the gas.

Hold a piece of damp red litmus paper over the mouth of the test tube. The ammonia gas will turn the damp red litmus paper blue indicating its presence. Ammonia hydroxide is formed on the damp red litmus paper, as it has became an alkali, it turns the damp red litmus paper blue

#1

Zinc Nitrate (NO3-) reacts with Aqueous Ammonia (NH4OH) to form a SALT and a BASE

(i) Name the salt and the base

The salt produced in this reaction is Ammonium Nitrate (NH4)2NO3
The base formed is Zinc Hydroxide (ZnOH)

(ii) Describe the observations for the reaction

The previously-colourless solutions remain colourless (due to the formation of Ammonium Nitrate) and there is a presence of white precipitate (the insoluble Zinc Hydroxide)

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

ZnNO3 (aq) + 2NH4OH (aq) à Zn(OH)2 (s) + (NH4)2NO3 (aq)


(iv) Write an ionic equation for the reaction


Zn2 + (aq) + 2OH- (aq) à  Zn(OH)2 (s)