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?
To ensure that the Hydrochloric Acid and Zinc Carbonate is completely reacted.
(iii) Briefly explain how the zinc chloride crystals can be obtained.

We filter to remove the excess unreacted Zinc Carbonate solid. Evaporate the solution to remove the water and make a saturated salt solution. The hot saturated solution form Zinc Chloride crystals when it is cooled.

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.
The salt is Group I salt, hence it's method is titration.
(ii) Write an ionic equation for the reaction.
H+ (aq) + OH- (aq) > H2O (L)

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.
The gas is Ammonia.
(ii) This is a confirmatory test for an anion. Name this anion.
The anion is Nitrate.
(iii) Give a possible cation which gives the green solution.
Iron ll.

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.
The gas will turn damp red litmus paper blue.

Qn1. 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 while the base is Ammonium Nitrate.
(ii) Describe the observations for the reaction.
They they react with each other, 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)

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5. Sodium is a metal and sulfur is a non-metal....why we classify them this way??

Sodium is a metal as it have 1 electron to complete it's valance shell, conduct electricity and have lower electronegativities . Electronegativity is a measure of the ability of an atom in a molecule to draw bonding electrons to itself.





















Electronegativity information and above picture are from :
http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/metal.html
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bondd.html#c3

Sulfur is a non-metal as it gain 2 electrons to complete it's valance shell, does not conduct electricity and have higher electronegativities.

Group (I), (II) and (III) are metals while Group (IV), (V), (VI) , (VII), (VIII) and Group 0 are non-metal. Sodium fall on Group (I) while sulfur fall on (VI).


















Above picture is from :
http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/metal.html