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) Salt: Ammonium nitrate
Base: Zinc hydroxide

(ii)A white precipitate of zinc hydroxide Zn(OH)2 is formed.

(iii)

(iv)

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)

(ii) Turns damn 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. (ii) This is a confirmatory test for an anion. Name this anion. (iii) Give a possible cation which gives the green solution.

(ii)Nitrate


(iii)Iron (II), Fe2 +

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 use to prepare Group(I) salt. (soluble salt)

(ii)

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)

(ii) To ensure that all the hydrochloric acid is completely reacted with the zinc carbonate.

(iii)

Step 1: Add excess zinc carbonate solid to beaker of dilute hydrochloric acid until there is excess white zinc carbonate solid left behind.
Step 2: Filter to remove the excess unreacted zinc carbonate solid.
Step 3: Evaporate the zinc chloride solution to remove water and make a saturated salt solution.
Step 4: The hot saturated solution form zinc chloride salt when it is cooled.

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


Atom have a shape similar to a sphere and is make by the negatively charge electrons which is surround by the positive charge nucleus.

The sub-atomic particles inside an atom are proton, neotron and electron.

Electrons: one of the subatomic particles that are present in an atom and carrying a negative charge(-). They form an electron clouds which surround the nucleus. An electron has a mass approximately 1/1836 to the mass of a proton. Electrons are mainly found in the region known as electron shells and they are involved in chemical reaction through sharing or transferring from one atom to another.

Protons : are one of the subatomic particles that are present in the nucleus of the atom and carrying a positive charge(+). Each proton has a mass of 1 amu (atomic mass unit). The number of protons present in the nucleus also known as atomic number which identify the chemical elements that the atom belongs to. Proton is also relatively stable as it is being given out by the acid in water.

Neutrons: are one of the subatomic particles that are present in the nucleus of the atom and carrying no electric charge. Each neutron has a mass of 1 amu. The number of the neutrons present in the nucleus may affect the stability of the atom and atom having the same number of protons but different numbers of neutrons is known as isotopes.

Electrons shells : the region where electrons are being found in the atom. Each electrons shell has different energy level and has a fixed number of electrons that can be present. The electrons are generally occupying the shell of a lowest energy first before filling up the rest of the electron shell. The electrons in the last electron shell are known as outermost shell or valence shell. Most chemical reactions involving the electrons in the valence shell. A complete filled valence shell will provide the atom stability. Atoms lose or gain electrons to obtain the complete outermost electrons shell which make the atom stable. One group of elements which have a complete valence shell is known as noble gases.

Nucleus: a positive charge(-) and present at the center of the atom. Nucleus consists of protons and neutrons. An unstable nucleus may cause radioactive decay to form the stable nucleus. However, the number of protons and neutrons in the nucleus doesn’t affect the chemical properties of the atom as it is much depend on the electrons in the valence shells.




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

The sodium atom have 11 electrons. The innermost shell can only consists up to a max of 2 electrons , while the other shells can consists up to a max of 8 electrons .

Sodium ion has to give away 1 electron to complete the valence shell, so as to make it stable .

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

Sulphur has an electronic configuration of 2.8.6. Sulphur require to gain 2 electrons to complete the valence shell and make it stable.

When the sulphur atom gain 2 electrons, the atom have a charge of (-2) .

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

Isotopes(definition):

1) Different atoms of the same element which have the same number of proton but different number of neutrons.

2) Different atoms of the same element which have the same protons number but different mass number.

Both chlorine have the same number of protons-17. However, one of the chlorine has 18 neutron while another one has 20 neutrons. Hence, they are isotopes.




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

Sodium metal lose electrons to form electrons around the cations. The electrons are able to carry the electric charge.

Hence the metal is a good conductor of electricity. Sodium metal obtain full valence shell through losing 1 electron. Sulphur gain 2 electrons to form anions. and usually form covalent bonding through sharing.

Sulfur is a non-metal. Thus, it gain 2 electrons to complete the valence shell to make it stable.