Chemistry JAMB, WAEC, NECO AND NABTEB Official Past Questions

All your burette readings (initial and final), as well as the size of your pipette, must be recorded but on no account of experimental procedure is required. All calculations must be done in your answer book.

(a) Put A into the burette and titrate it against 20.0 cm\(^3\) or 25.0 cm\(^3\) portion of B using methyl orange as indicator. Record the volume of your pipette. Tabulate your burette readings and calculate the average volume of A used. The equation for the reaction is 2NaOH\(_{(aq)}\) + H\(_2\)X\(_{(aq)}\) \(\to\)  2H\(_2\)O\(_{(l)}\) 

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

(i) Concentration of solution B in mol dm\(^{-3}\) 

(ii) concentration of solution A in mol dm\(^{-3}\)

(iii) molar mass of the acid H\(_2\)X. [H = 1, O = 16, Na = 23] 

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

C is a mixture of two inorganic compounds. Carry out the following exercises on C. Record your observations and identify any gases evolved. State the conclusion you draw from the result of each test.

(a) put all of C into a beaker and add about 10cm\(^3\) of distilled water. Stir thoroughly and filter. Keep both the residue and the filtrate

(b) Divide the filtrate into three portions.

(i) To the first portion, add sodium hydroxide solution in drops until ít is in excess. 

(ii) To the second portion, add aqueous ammonia in drops until it is in excess.

(iii) To the third portion, add about 2cm\(^3\) of barium chloride solution, followed dilute hydrochloric acid in excess.

(c) Put the residue in a test tube and add about 2cm\(^3\) of dilute tetraoxosulphate (VI) acid. Shake the mixture and warm.

(i) Add aqueous ammonia in drops to the mixture from (c) (i) above until it is in excess.

(a) List two gases in each case which;

(i) can be used to demonstrate the fountain experiment;

(ii) decolourize acidified potassium tetraoxomanganate (VII).

(b) State briefly how you would distinguish between

(i) crystals of PbCO\(_3\) and Pb(NO\(_3\)) using heat;

(ii) solutions of NH\(_4\)CI and NaCl using litmus paper.

(c) Mention two changes that would be observed on adding moderately concentrated hydrochloric acid to iron filings

(a)(i) List two elements which react with steam at red heat to produce hydrogen.

(ii) Explain why an aqueous solution of potassium bromide turned reddish brown on bubbling chlorine through it.

(iii) Write an equation for the reaction in (a)(ii).

(b)(i) Name two types of chemical industry that use limestone as raw material.

(ii) Give one example of hygroscopic substances.

(iii) Copy and complete the table below.

(c) In the contact process for the manufacture of tetraoxosulphate (VI) acid;

(i) State how sulphur (IV) oxide is obtained;

(ii) Write an equation for the reaction that takes place in the catalyst chamber;

(iii) Give the steps required to convert sulphur (VI) oxide to acid.

(d)(i) List two disadvantages of hard water.

(ii) Mention three methods which can be used to remove both permanent and temporary hardness in water at the same time.

(iii) State the role of alum and chlorine respectively in the purification of water for town supply.

(a)(i) Define allotropy.

(ii) Name the allotrope of carbon used in gas masks.

(iii) Mention two other elements which exhibit allotropy apart from carbon.

(b) List the products of each of the following reactions:

(i) Heating coal in the absence of air.

(ii) Burning of candle wax in plentiful supply of air

(c)(i) State the two properties of carbon (IV) oxide which make it useful in extinguishing fire.

(ii) Write an equation for the reaction of carbon (IV) oxide with lime water

(iii) Calculate the volume of oxygen that was in excess if 150cm\(^3\) of carbon (II) oxide was burnt in 80cm\(^3\) of oxygen according to the following equation: 2CO\(_{(g)}\) + O\(_{2(g)}\) \(\to\) 2CO\(_{2(g)}\).

(d)(i) State how nitrogen can be obtained from ammonia gas.

(ii) Name the gaseous fuels obtained when steam and air are passed over red hot coke.

(iii) Which of the fuels in (d)(ii) has the lower heating ability? Give reason for your answer.

(a)(i) Give two differences between a conductor and an electrolyte.

(ii) State three applications of electrolysis.

(iii) Write equation for the reaction at each electrode when a dilute solution of sodium chloride is electrolysed using carbon electrodes.

(b)(i) What is an electrochemical cell?

(ii) Give two examples of primary cells.

(iii) Split the following equation into two balanced hall cell equations. Mte + Fe\(^{2+} \to Mg^{2+} + Fe\).

(c)(i) A current of 0.72 amperes was passed through dilute tetraoxosulphate (VI) acid for 3 hours 20 minutes. Calculate the quantity of electricity that was passed

(ii) If 1 dm\(^3\) of gas evolved at the cathode during the electrolysis of acidified water, what was the volume of gas evolved at the anode?

(d)(i) 20g of copper(II) oxide was warmed with 0.05 mole of tetraoxosulphate (VI) acid. Calculate the mass of copper (II) oxide that was in excess. The equation for the reaction: CuO\(_{(s)}\) + H\(_2\)SO\(_{4(aq)}\) —> CuSO\(_{4(aq)}\) + H\(_2\)O\(_l\) [0 = 16 ; Cu = 64]

(ii) What type of reaction was involved in (d)(i)?

(a) The letters R,S,T represent an alkene, an alkene and a terminal alkyne respectively. Which of R, S and T typically undergo(es) the following reactions?

(i) Addition reaction;

(ii) Combustion;

(iii) Substitution reaction.

(b)(i) Name the process by which an alkanol can be converted to an alkene.

(ii) Write the name and structural formula of the third member cf the alkanol series.

(iii) State what would be obtained if a primary alkanol reacted with excess acidified KMnO\(_4\) solution.

(c)(i) Give one chemical test for alkanoic acids.

(ii) Write an equation to show how methanoic acid reacts with ethanol in the presence of mineral acids.

(iii) What is the role of mineral acid in the reaction in (c) ii?

(d) In an experiment, cassava was pressure-cooked to release starch granules, followed by treatment with malt for about 2 hours at 55°C. Yeast was then added and the mixture was left for 2 days at 27°C. An organic product J and a gas H were obtained.

(i) Identify H

(ii) State the class of carbohydrates to which starch belongs and explain what happened to the starch during treatment with malt.

(iii) Draw a labelled diagram of a suitable set-up for obtaining a sample of J from the reaction mixture.

a)(i) State three differences between covalent compounds and electrovalent compounds.

(ii) Two elements represented as K and L have atomic numbers of 12 and 8 respectively. Write their electronic structures and state the group to which each belongs in the Periodic Table.

(iii) If an alkali metal M exists naturally as the oxide, state with reason whether or not M can be extracted by reduction of the oxide with coke.

(b)(i) What is meant by the half-life of a radioactive element?

(ii) Mention the radioactive isotope used in dating archaeological specimens.

(iii) Balance the following equation and identify Q,

\(^{28}_{13}Al\) —> \(^{24}_{13}Si + \(^{0_1Q\)

(c)(i). Give three chemical properties of metals.

(ii) State two reasons why duralumin preferred to steel in aircraft manufacture.

(iii) What term is used to describe the ability of metals to be hammered into thin sheets?

(iv) Calculate the number of mole of electrons involved in the oxidation of 2.8g of iron filings to iron (II) ions. [Fe = 56].

(a)(i) State three postulates of the kinetic theory of gases.

(ii) Draw a sketch to illustrate Boyle’s law.

(iii) Explain what is meant by “absolute zero of temperature”.

(b) Equal volumes of a gas X and oxygen are at the same pressure but temperature of 200 K and 800K respectively.

(i) Giving reason for your answer, state which of the gas samples contains the greater number of molecules.

(ii) If the mass of one molecule of the gas X is 2.19 x 10\(^{-22}\) g, determine the molar mass of X. [Avogadro constant = 6.02 x 10\(^{-23}\)]

(iii) Hence, state with reason which of X and oxygen will diffuse faster under the same conditions. [O= 16].

(c)(i) Mention two reaction conditions that can increase the yield of ammonia in the reaction represented by the following equation: N\(_{2(g)}\) + 3H\(_{2(9)}\) \(\rightleftharpoons\) 2NH\(_{3(g)}\) \(\Dellta\)H = -46kJmol\(^{-1}\). Draw a labelled energy profile diagram for an endothermic reaction.

(iii) A solid W decomposes on heating according to the following equation: W\(_{(s)} \to  Y_{(s}) + Z_{(g)}\) List two factors apart from temperature, which can affect the rate of the reaction.

The greenhouse effect is a climatic condition associated with the presence of excess

Environmental pollution problems are generally more severe in countries which have

Which of the following is needed to produce slag during the extraction of iron in the blast furnace?

Geometric (cis-trans) isomerism is exhibited by

Which of the following is a secondary alkanol?

Alkanoates are produced from alkanols by

Which of the following compounds reacts with sodium hydroxide to form a salt?

Which of the following compounds is unsaturated?

Which of the following is the most reactive towards bromine?

How many carbon atoms are present in one molecule of 2-methylpropane?

When dilute copper (ll) chloride solution is electrolysed, the reaction at the cathode is represented by the equation

Equal volumes of water were added to one mole of each of the following compounds. Which of them produced the largest number of ions