Chemistry JAMB, WAEC, NECO AND NABTEB Official Past Questions

Burette readings (initials and final) must be given to two decimal places. Volume of pipette used must also be recorded but no account experimental procedure is required. Al calculations must be done in your answer book. A solution containing 0.05moldm\(^3\) H\(_2\)SO\(_4\). B is a solution containing 1.4g per 250cm\(^3\) .XOH  

(a) Put A into the burette and titrate it against 20.0cm\(^3\) or 25.0cm\(^3\) portions of B using methyl orange indicator. Repeat the titration to obtain consistent titres. Tabulate your results and calculate the average volume of A used. The equation for the reaction involved in the titration is; H\(_2\)SO\(_{4(aq)}\) + 2XOH\(_{(aq)}\) \(\to\) X\(_2\)SO\(_{4(aq)}\) + 2H\(_2\)O\(_{(l)}\)

(b) From your results and the information provided above, calculate the;

(i) concentration of B in moldm\(^{-3}\)

(ii) molar mass XOH

(iii) relative atomic mass of X. [H = 1.00; O = 16.0 S =32.0]

Credit will be given for strict adherence to the instructions, for observations precisely recorded, and for accurate inferences. AIl tests. observations and inferences must be clearly entered in your answer book, in ink, at the time they are made.

C is a double salt. Carry out the following exercises on C. Record your observations and identify any gas(es) evolved. State the conclusion drawn from the result of each test.

a) Put all of C into a test tube. Add about 5cm\(^3\) of distilled water, stir and test with litmus paper. Divide the Solution into two portions

(b) To the first portion, add sodium hydroxide solution in drops and then in excess. Heat the resulting mixture and keep it for minutes.

(c) To the second portion, add few drops of Bacl\(_{2(aq)}\) followed by excess dilute hydrochloric acid

(a)i) How would an aqueous solution of iron (II) tetraoxosulphate (VI) be converted into an aqueous solution of magnesium tetraoxosulphate (VI)?

(ii) Write a balanced equation for the reaction in (a)(i) above

(b)(i) Why are some compounds recrystallized after preparation?

(ii) Outline the steps in recrystallization

(C)(i) Name two gases that can cause color changes in an acidified solution of potassium heptaoxodichromate (VI)

(ii) State the color change expected in (c)i) above

(a)(i) List two characteristics of homologous series.

(ii) Consider the compound represented by the following formula: CH\(_3\)(CH\(_2\))\(_2\)CH\(_3\). I. Which homologous series does the compound belong? II. Write the structures of three possible isomers of the coumpound. III Name the three possible isomers in (a)(ii)II.

(b) Write the structure of the major product formed in each of the following reactions: (i) ethanol with excess acidified potassium tetraoxomanganate (VII);

(ii) excess ethane with chlorine in the presence of sunlight;

(iii) ethanol with propanoic acid in the presence of few drops of concentrated tetraoxosulphate(VI) acid.

(c) Name the major product in each reaction in (b).

(d) Consider the following organic compounds:

(i) Give the IUPAC name of each compound.
(ii) State a chemical test for the functional group in each compound.

(e) An organic compound with relative molecular mass 136 contains 70.57% carbon, 5.90% hydrogen and 23.53% oxygen. Determine its: (i) empopirical formula; (ii) molecular formula. [H= 1.00, C= 12.0, H = 16.0]

(a)(i) Explain briefly the term chemical industry.

(ii) State three factors that should be considered in siting a chemical industry.

(b)(i) Describe briefly twin is extracted from its ore.

(ii) Give two uses of tin.

(c)(i) Name the constituents of cement.

(ii) How does mortar set?

(d)(i) Explain briefly the term pollution.

(ii) Give two examples of air pollutants.

(e) Consider the following reversible reaction which occurred at the temperature of 298K:

N\(_{2(g)}\) + 3H\(_{2(g)}\) \(\rightleftharpoons\) 2NH\(_{3(g)}\); \(\bigtriangleup\)H = —92.37kJ

(a)(i) Define the term hygroscopic.

(ii) Give two difference: between a physical change and a chemical change.

(iii) Using the kinetic theory of gases, explain briefly the Charles’ law.

(b)(i) Arrange the following compounds in order of increasing boiling points: CS\(_2\); CO\(_2\); NaH. Give reasons for your answer.

(ii) Write a balanced chemical equation to illustrate the reaction of chlorine gas with cold dilute sodium hydroxide.

(c) In a certain reaction, 15.0 g of impure magnesium sample reacted with excess hydrochloric acid liberating 8.6 dm\(^2\) of hydrogen gas at s.t.p.

(i) Write a balanced equation for the reaction.

(ii) Calculate the: I. mass of pure magnesium in the sample; I. percentage purity of the magnesium sample; III. number of ions produced in the reaction. [Mg = 24.0; volume at s.t.p. 22.4 dm\(^{-3}\), Avagadro’s constant = 6.02 x 10\(^{23}\)mol\(^{-1}\)]

(a)(i) Define the term standard electrode potential.

(ii) State three factors that affect the discharge of ions during electrolysis.

(iii) State two functions of a salt bridge in an electrochemical cell.

(b) Describe briefly what happens when a solution of copper (II) tetraoxosulphate (VI) is electrolyzed using copper electrodes.

c) Calculate the mass of copper deposited at the cathode when a current of 0.2A is passed through a solution of copper (II) tetraoxosulphate (VI) for 35 minutes using copper electrodes. [H = 1.00, O = 16.0, S = 32.0, Cu = 64.0, IF = 96,500C]

(d)(i) State three characteristics of a catalyst.

ii) Name one manufacturing process in which each of the following metals is used as catalyst: I. iron; II. nickel; Ill. platinum.
c-NA

(a)(i) Define each of the following terms: I. normal salt. II. acid salt.

(ii) Tetraoxosulphate (VI) acid and sodium hydroxide react to produce salt and water. Write a balanced chemical equation fir the formation of: I. a normal salt; II. an acid salt.

(b)(i) Explain briefly the term acid-base indicator.

(ii) Copy and complete the following table.

(iii) For each of the following titrations, state the most suitable indicator: I. strong acid against strong base; II. strong acid against weak base; iii. weak acid against strong base.

(c) Baking soda and hydrochloric acid react according to the following equation:

NaHCO\(_{3(aq)}\) + HCI\(_{(aq)}\) —> NaCl\(_{(aq)}\) CO\(_{2(g)}\) + H\(_2\)O\(_{(l)}\). Calculate the mass of baking soda that would produce 10g of ccrbon (IV) oxide. [H = 1.00, C = 12.0, 0 = 16.0, Na = 23.0]

(d) Give a reason why a given mass of sodium hydroxide pellets cannot be used to prepare a standard solution.

NaHCO\(_3\) + HCI –> NaCI + CO\(_2\) + H\(_2\)O

84g NaHCO\(_3\)  –> 44g CO\(_2\)

Xg –> 10g CO\(_2\)
Xg = \(\frac{84 \times 10}{44}\)

= 19.09g

= 19.1g.

(d) give a reason why a given mass of sodium hydroxide pellets cannot be used to prepare a standard solution: Sodium hydroxide absorbs water/deliquescent and absorbs carbon IV oxide from air/and this would make mass taken unreliable/add to its mass.

(a)(i) What is the common name given to the group VII elements?

(ii) Name the hydrides of the first two elements in group VII.

(iii) State three chemical properties of group VII elements.

(b) Copy and complete the following table:

(c)(i) Define each of the followinc processes: I. nuclear fission; II. nuclear fusion.

(ii) Give one use of each process in (c)(i).

(d)(i) List three types of radiation that are produced during radioactivity.

(ii) Arrange the radiations listed in

(d)(i) in order of increasing: I. penetrating power; II. ionizing power.

Which of the following statements about thermoplastic material is correct? They

Bronze is a mixture of

Which of the following materials is classified as a non-biodegradable pollutant?

Which of the following statements about fine chemical is correct? It

Which of the following raw materials is used in a plastic industry?

The main function of limestone in the blast furnace is to

A hydrocarbon compound contains 92.3% carbon Determine its empirical formula [H = 1.00; C = 12.0]

Which of the following reactions is common to all hydrocarbones?

How many isomers has C ₃H ₆CI ₂?

Which of the following organic compounds would decolourize bromie water?

The major product formed by the reaction between ethanoic acid and aqueous sodium hydroxide is

The separation of petroleum fractions depends on the differences in their