Waec Chemistry 2005 Past Questions and Answers

Question 41:

• WAEC 2005

(i) Write the structure of 2—chloro-2—methylpropane.
(ii) Consider the compound X represented by the structure below:

I. State the functional group in X; II. Give the IUPAC name of X; Ill. State the homologous series to which X belongs. IV. Give the names of two compounds from which X is formed. V. State one physical characteristt of X.

(b)(i) List two products obtained from fractional distillation of petroleum;
(ii) State one use of each product in (b)(i) above,
(iii) Mention one disadvantage of crude oil production

(c)(i) Mention the monomer of protein (ii) A compound has an empirical formula of CHO\(_2\) and its molar mass is 90. Deduce the molecular formula of the compound. [H = 1, C = 12, O = 16].

(d) Use the reaction scheme below to answer questions (i).— (iv).

(i) State the reagents needed for stages II and V;
(ii) Nanie the product Q of reaction in stage IV;
(iii) State the conditions required for stage III;
(iv) Give the names of the processes in stages I, II, Ill and V respectively.

Question 42:

• WAEC 2005

(a)(i) List three observable changes that take place when a dilute solution of copper (II) chloride is electrolysed using platinum electrodes. Stage III
(ii) Calculate the quantity of electricity used during electrolysis when a current of 0.21 ampere flows for 2 hours.
(iii) State what is meant by the term preferential discharge of ions in electrolysis
(iv) Give one factor which influences the preferentia! discharge of ions during electrolysis.
(v) State one Q difference between-a conductor and an electrolyte.

(b) Consider the reaction represented by the equation below: Na\(_2\)S\(_2\)O\(_{3(aq)}\) + 2HCI\(_{(aq)}\) \(\to\) 2NaCI\(_{(aq)}\) + H\(_2\)O\(_{(l)}\) + SO\(_{2(g)}\) + S\(_{(s)}\)
(i) List two factors that can affect the rate of this reaction.
(i) Which of the products can be readily used to measure the rate of the reaction. Give a reason for your answer.
(iii) Name two instruments that can be used to measure factors in (b)(i) above.

(c)(i) State the reasons for regarding rusting and burning as oxidation processes.
(ii) I. Write the balanced half equations for the following redox reaction: Mg\(_{(s)}\) + Fe\(^{2+}_{(aq)}\) ----> Mg\(^{2+}_{(aq)}\) + Fe\(_{(s)}\)
II. Which of the reactants is the oxidizing agent?
Ill. State the change in the oxidation number of the oxidizing agent.

(d)(i) State one ore from which each of the following metals can be extracted. I. Tin II. Iron (ii) List two uses of copper (iii) Name one alloy of tin.

Question 43:

• WAEC 2005

(a)(i) State the two types of hardness in water.
(ii) Name a salt that causes each type of hardness.
(ii) Write a balanced equation for the removal of each type of hardness.
(iv) State one effect of hard water on soap.

(b)(i) State whether the pH of each of the following is less than, equal to, or greater than 7.
I. Glucose solution II. Chlroine water III. Lime water IV. Sour milk
(ii) Give the difference between the following compounds: I. an acidic oxide and an amphoteric oxide; II. concentrated acid and a dilute acid; Ill. a normal salt and an acid salt

(c)(i) Iron reacts with H\(_2\)SO\(_4\) according to the equation: Fe\(_{(s)}\) + H\(_2\)SO\(_{4(aq)}\) ---> FeSO\(_{4(aq)}\) + H\(_{2(g)}\)
Calculate the mass of FeSO\(_4\) that would be produced by 0.5 mole of Fe. [H = 1, S = 32, Fe = 56]
(ii) List two allotropes of sulphur

(d)(i) State what would La observed when a damp starch-iodide paper is dropped into a gas jar of chloride
(ii) Explain your ansv.er in (d)(i) above.
(iii) State the products formed when ammonia reacts with excess chlorine.