Question 5

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

i) Normal Equation: ZnCO3(s) + 2H⁺Cl⁻ (aq) ---> Zn²⁺Cl⁻2 (aq) + H2O (L) + CO2 (g)
Ionic Equation: ZnCO3(s) + 2H⁺(aq) ---> Zn²⁺(aq)  H2O (L) + CO2 (g)


ii) Excess Zinc Carbonate will ensure that the hydrochloric acid is completely reacted.


iii) After adding Zinc Carbonate to hydrochloric acid until excess zinc carbonate is seen. we then filter these excess zinc carbonate out using a filter funnel and at the same time transfer the solution( ZnCl2) to a beaker. Evaporated the solution to remove water till its a saturated solution. When cooled the zinc chloride crystals will formed and can be obtained.

Question 4.

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.  (ii) Write an ionic equation for the reaction.

i) Titration is used for soluble Group(I) or ammonium salts, since potassium is an element from Group(I) and is also soluble titration is used to prepare its salt.


ii) Normal Equation: 2K⁺OH^- (aq) + H⁺2SO4²⁻(aq) ---> K2⁺SO4²⁻(aq) + 2H20 (L)
Ionic Equation: 2OH^- (aq) + H⁺2 ---> 2H20 (L)

Question 3

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. (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)  nitrate


iii)  iron(ii)

Question 2

Q2 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. 

i) (NH4)2SO4 (aq) + 2NaOH (aq) ---> Na2SO4 (aq) + 2H20 (L) + 2NH3 (g) 


ii) Use damp red litmus paper on gas and it will turn blue if its NH3.

Question 1

Q1 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.  


i)The Salt is Ammonium Nitrate. The Base is Zinc Hydroxide.


ii)A white precipitate is formed during the reaction.


iii)Zn(NO3)2(aq)  + 2NH4OH(aq) ---> 2NH4(NO3)(aq) + Zn(OH)2 (s)


iv)Normal Equation:Zn²⁺(NO3)-2(aq)  + 2NH4⁺ OH-(aq)--->2NH4

⁺

(NO3) ⁻(aq) + Zn(OH)2 (s)
Ionic Equation:Zn²⁺ (aq) + 2OH^- (aq) ---> Zn(OH)2 (s)

Comments

Xin Kang
Hi Xin Kang!!!=) Guess I'll just post mu comments here too... Well, Overall I think the answers are good and easy to understand butshould't the relative mass of electrons be 1/1840?0.0And i told you in school before but you explanation in Q.3 is Sulfide ion not Sulfur ion=) Please comment on my too!!The last comment is sure to get you 1 mark you know XD
ZW
Helmi
Hi Helmi! Here are my comments for your answers. Firstly, i really like the picture from the website you posted in question 2(really clear and easy to understand)^^. Your answers are detailed and imformative. And of course it jolted my memory on anions which i had forgotton about.
ZW
Fabian
Hi Fabian! Comments on your answers are here!=) For Q.5 your first comparision on why sodium is metal and sulfur a non-metal was very good i didn;t think of that answer before i read yours. For question 1 there are no problems with it but i would't hurt to list down to relative mass too.=)

ZW

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