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 Ammonium nitrate and the base is Zinc hydroxide.

(ii) Desribe the observation for the reaction.

When zinc nitrate reacts with the aqueous ammonia, white precipitate is form and it is soluble in excess to give a colourless solution.

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

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

(iv) Write an ionic equation for ther reaction.

Zn^2+ (aq) + 2OH- (aq) -> Zn(OH)2 (s)

Qn2) Ammonium sulfate is heated with sodium hydroxide.

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

(NH4)2SO4 (aq) + 2NAOH (aq) -> NA2SO4 (aq) + 2H2O + 2H3 (g)

(ii) Describe a test for the gas.

It turns damp red litmus paper to blue.

Qn3) 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.

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

Nitrate.

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

Iron (II) ions.

Qn4) Sulfuric acid is titrated with potassium hydroxide in the preparation of potassium sulfate salt.

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

As potassium hydroxide is a group I soluble salt, therefore, tiltration is recommended for the preparation of this salt.

(ii) Write an ionic equation for the reaction.

H+ (aq) + OH- (aq) -> H2O (l)

Qn5) 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) + H2O (l) + CO2 (g)

(ii) Why is excess zinc carbonate used?

To ensure that the zinc carbonate and hydrochloric acid is fully reacted before filtering out the excess unreacted solid from the salt solution.

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

Zinc carbonate will be added to the hydrochloric acid first till it is fully reacted and the excess solid is left behind. Then filtrate the zinc chloride solution to remove the excess unreacted solid. Remove the water to make a saturated sat solution, by using evaporation. The hot saturated solution is then left to be cooled to obtain the zinc chloride crystals.

#1 Aleen (27)
Her blog is full of imformation and her explaination is very clear, she has done lots of research. Her answers were very detailed. One mistake she made was that for her drawing for sodium ion, the charge should be '+' instead of '1+'. Overall, i find it easy to understand her answers (: Nice blog(:

#2 Xueting (19)
Her answer is clear and she made an effort to use the compass to draw the elements and ions to make her work neat. She still provide extra information which allows me to recall my basic facts (: Nice blog too(:

#3 Wanling (16)
Her answer is easy to understand and she highlighted the key points that make me understand her explainations easier. I think one of the drawings for sulfide ion, the charges should be outside the shell. and it should be 'sulfide ion' instead of 'sulfur ion'? (: other than the answers, she also posted lots of videos, it is very nice! :P I enjoy reading her blog! (:








Ans 5) Sodium metal and sulfur is a non-metal... Why do we classify them in this way?








Ans 4) Chlorine-35 atom and Chlorine-37 atom are called isotopes... Use these two examples to explain what is 'isotopes'.

Defination of iostopes, different atoms of the same element which have the same number of protons but different number of electrons.

Chlorine-35 have a proton and neutron no. of 35.
Chlorine-37 have a proton and neutron no. of 37.
Both have the same number of 17 protons.
Chlorine-35 has 18 neutrons (35-17=18)
Chlorine-37 has 20 neutrons (37-17=20)

Therefore, Chlorine-35 and Chlorine-37 are isotopes.

Ans 3) Draw the atomic structure of a sulfur atom and a sulfide ion... Explain why you draw it in this way. Sulfur has a valency of 6. Sulfur needs to accept two electrons to achieve a full shell (2.8.8). When sulfur gains two electrons, sulfide ion is formed.

- I drew it myself.

Ans 2) Draw the atomic structure of a sodium atom and a sodium ion... Explain why you draw it this way.
Sodium has a valency of 1. Sodium needs to give away one electron to achieve a full shell (2.8). When sodium loses one electrons, an sodium ion is formed.

-I drew it myself.

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