Q1 Zinc nitrate reacts with aqueous ammonia (NH4OH) to form a salt and a base. 
(i) Name the salt and the base.
Salt:zinc nitrate
Base: zinc hydroxide.

(ii) Describe the observations for the reaction.
white precipitation is formed, soluble in excess giving a colourless solution.

(iii) Write a chemical equation for the reaction (include state symbols).
Zn(NO3)2   (aq)  +  2NH4OH (aq)  -->  Zn(OH)2 (s)  +  2NH4NO3 (aq)

 (iv) Write an ionic equation for the reaction. 
Zn2+ (aq)  +  2OH- (aq)  -->    Zn(OH)2 (s)

Q2 Ammonium sulfate is heated with sodium hydroxide.
(i) Write a chemical equation (include state symbols) for the reaction. 
(NH4)2SO4 (aq) +  2NaOH (aq)  -->  2NH3 (g) + Na2SO4 (aq) + 2H2O  (L)

(ii)  Describe a test for the gas.
It turns damp red litmus paper blue.

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

(ii) This is a confirmatory test for an anion.  Name this anion. 
Nitrate (NO3-) in solution

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

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 hydroxide and sulfuric acid and potassium sulfate salt are all soluble and colourless solutions so titration is the best method.

(ii) Write an ionic equation for the reaction.
H+ (aq) + OH- (aq)  --> + H2O (L)

Q5 Excess zinc carbonate is added to hydrochloric acid in the preparation of zinc chloride salt.
(i) Write an ionic equation for the reaction.
(CO3) 2- (aq) + 2H+ (aq) --> H2O (L) + CO2  (g)

(ii)  Why excess zinc carbonate is used?
Excess is used to ensure that it has completelty reacted with the hydrocloric acid.

(iii) Briefly explain how the zinc chloride crystals can be obtained.
Add excess zinc carbonate to a beaker of hydrochloric acid until there is excess zinc chloride left behind. Filter to remove the excess unreacted zinc carbonate solid. Then evaporate the zinc chloridesolution to remove the water and make a saturated solution. The hot saturated solution would form zinc chloride crystals when cooled.

1. What does an atom looks like? What are the sub-atomic particles inside it.....(talk about electrons, neutrons, protons, electron shells, nucleus....)

Ans: An atom consists of 3 sub-atomic particles and 1 nucleus. The 3 sub-atomic particles are: Protons; Neutrons and Electrons. Protons and Neutrons are found in the nucleus whereas electrons are found in the electron shell. An electron is negatively charged while a proton is positively charged. In an element, the number of electrons is the same as the number of protons. Whereas in an ion, the number of electrons and protons differs. The nucleon number or relative atomic mass number ( usually located at the top left hand corner of the element box ) is the relative mass of all the protons, neutrons and electrons in the element.

Sub-atomic Particles	Relative Mass
Electron	1 / 1840
Proton	1
Neutron	1

2. Draw the atomic structure of a sodium atom and a sodium ion....explain why you draw it this way.

Ans:

The sodium atom is drawn that way because its has 11 electrons and its electronic configuration is ( 2.8.1 ). Thus, it has 1 valence electron that determines its charge when it becomes an ion. The sodium ion is drawn in such a way because it has given away 1 valence electron in order to become stable during a reaction. Thus, its electronic configuration is now ( 2.8 ) and its charge is +1.

3. Draw the atomic structure of a sulfur atom and a sulfide ion....explain why you draw it this way.

Ans:

The sulfur atom is drawn that way because its has 16 electrons and its electronic configuration is ( 2.8.6 ). Thus, it has 6 valence electron that determines its charge when it becomes an ion. The sulfide ion is drawn in such a way because it has gained 2 valence electron in order to become stable during a reaction. Thus, its electronic configuration is now ( 2.8.8 ) and its charge is -2.

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

Ans:

Chlorine Atoms	No. of Proton	No. of Electron	No. of Neutron
Chlorine-35	17	17	18
Chlorine-37	17	17	20

Isotopes are different atoms of the same element that have the same number of proton, electron but different number of neutron. Since Chlorine-35 and Chlorine-37 have the same number of proton, electron but different number of neutron, they are isotopes of chlorine. Thus, the average nucleon number of chlorine is [(75/100) x35 ] + [(25/100) x37]


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

Ans: Sulfur is a non-metal because it does not conduct electricity and it will gain 2 electrons to complete the valence shell to make it stable during a reaction. Sodium is a metal because it conducts electrocity and it will lose 1 electron to complete the valence shell to make it stable during a reaction