O Level Chemistry Practice Questions

Chemistry Practice Questions (No answers will be given)

1.            Zinc chloride can be removed by reacting it with sodium carbonate.

                        ZnCl₂ (aq) + Na₂CO₃ (aq) --> ZnCO₃ (s) + 2NaCl (aq)

(a)          State the name for this type of reaction.

(b)          Construct an ionic equation for the above reaction.

(c)          Suggest how zinc carbonate can be removed from the mixture.

2.            Lithium, atomic number 3, is an element in Group I.

(a)          Describe what you observe when a small piece of lithium is added to water, followed by the addition of universal indicator.

(b)          Lithium fluoride is a crystalline solid with a high melting point.

                Explain why the melting point of lithium fluoride is high.

(c)          Caesium, atomic number 55, is another element in Group I.

            State

(i)            the number of electron shells an atom of caesium possesses,

(ii)          formula of caesium iodide,

(iii)         name of product of the reaction between caesium and oxygen.

3.            The Blast Furnace produces pig iron from haematite.

(a)          Besides haematite and coke, what is the other raw material A fed into the Blast Furnace?

(b)          Explain using equations why A is added to the Blast Furnace.

(c)          Name the reducing agent that reduces iron(III) oxide to iron.

(d)          The iron produced by the Blast Furnace is converted into steel.

                        What is the composition of steel?

4.            State the separatory method that can separate the underlined substance:

(a)          pure water from seawater

(b)          a mixture of hexane and water

(c)          red ink from a mixture of red and black ink

(d)          heptane from a mixture of heptane and hexane

5.            Use the information in the table to answer the following questions.

Substance	Conducts electricity	Melting point /oC	Dissolves in water
A	No	808	Yes
B	No	113	No
C	Yes	3377	No
D	No	35-50	No
E	Yes	660	No

(a)          Which two substances could be metals?

(b)          Describe how the arrangement and movement of particles in E change as the temperature rises from 640^oC to 663^oC.

(c)          Is D a pure element, compound or a mixture? Explain briefly your answer.

(d)          What type of bonding could particles of A have?

(e)          Element B is sulfur. Explain why sulfur has a low melting point.

6.            Ethanol undergoes combustion with oxygen and oxidation with an oxidizing agent.

(a)          Write the balanced equation of ethanol reacting with oxygen.

(b)          The oxidizing agent used is acidified potassium dichromate(VI). State the product when ethanol is oxidized and the colour change of potassium dichromate(VI) after the reaction.

(c)          The product is extracted and litmus paper is placed in contact with the product. State the colour change of the litmus paper.

(d)          State a use of the product from (b).

7.            Carbon reacts with oxygen to form carbon dioxide.

(a)       Write the equation for the above reaction.

(b)       100 g of carbon reacts with an excess of oxygen to form carbon dioxide. Calculate the volume of carbon dioxide produced at room temperature and pressure.

(c)        Describe a test for carbon dioxide.

8.            Calcium reacts with water to form an alkaline solution.

Which set of conditions would give the fastest initial rate of reaction?

A         2 g of calcium at 25^oC

B         5 g of calcium at 5^oC

C         5 g of calcium at 25^oC

D         5 g of calcium at 40^oC

9.            The reaction below is an example of a redox reaction.

                        Br₂ (l) + H₂ (g) --> 2HBr (g)

(a)          Identify the oxidizing agent in the reaction.

(b)          Explain with reference to bromine and using oxidation number, why this is a redox reaction.

(c)          Ammonia gas reacts with hydrogen bromide, HBr to form a salt. Give the chemical name of the salt.