Chemistry JAMB, WAEC, NECO AND NABTEB Official Past Questions

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

A solution of 0.050 moldm\(^3\) H\(_2\)C\(_2\)O\(_4\) (ethanedioic acid). B is a solution of KMnO\(_4\), (potassium tetraoxomanganate (VII), of unknown concentration.

(a) Put B into the burette. Pipette 20.0 cm\(^3\) or 25.0 cm\(^3\) of A into a Conical flask and add about 10.0 cm\(^3\) of dilute H\(_2\)SO\(_4\), Heat the mixture to about 40°C – 50°C and titrate it while still hot with B. Repeat the titration to obtain consistent titre values. Tabulate your results and calculate the average volume of B used. The equation of reaction is;

2MnO\(_{4(aq)}^-\) + 5C\(_2\)O\(_{4(aq)}^{2-}\) + 16H\(^+_{(aq)}\) \(\to\)  2MnH\(^{2+}_{(aq)}\) + 8H\(_2\)O\(_{(l)}\) + 10CO\(_{2(g)}\)

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

(i) concentration of MnO\(_2^-\)  in B in moldm\(^{-1}\) 

(ii) concentration of KMnO\(_4^-\) in B in gdm\(^{-3}\)

(iii) volume of CO\(_2\) evolved at s.t.p when 25.0 cm\(^3\) of H\(_2\)C\(_2\)O\(_4\) reacted completely. [0 = 16.0, K= 39.0, Mn = 55.0, Molar volume of gas at s.t.p.= 22.4 dm\(^3\) mol\(^{-1}\)]

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

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

C is a mıxture of two salts, containing one cation and two anions. Carry out the following exercises on C. Record your observations and identify any gas(es) evolved. State the conclusion you draw from the result of each test.

(a) Put all of C in a beaker and add about 10 cm\(^3\) of distilled water. Stir well and filter. Keep the filtrate and the residue.

(b) To about 2 cm\(^3\) of the filtrate, add few drops of AgNO\(_{(aq)}\), followed by HNO\(_{3(g)}\). Add excess NH\(_{3(aq)}\) to the resulting mixture.

(c)(i) Put all of the residue into a clean test tube and add about 5 cm of HNO\(_{3(aq)}\)

(ii) To about 2 cm\(^3\) of the solution from 2(c)(i), add NaOH\(_{(aq)}\) in drops and then in excess

(iii) To another 2 cm\(^3\) of the solution from 2(c)(i), add NH\(_{3(aq)}\) in drops and then in excess.

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

(a) What difference in physical properties enable the separation of mixtures by:

(i) simple distillation,

(ii) paper chromatography;

(iii) fractional distillation.

(b) Give a reason for each of the following practices during titration in the laboratory.

(i) White tile is placed under the conical flask.

(ii) Burette readings are always recorded to two decimal places.

(iii) Calculate the volume of 2.5 moldm\(^{-3}\) stock HČI required to prepare 500 cm\(^3\) of 0.20 moldm HCI. 

(a)(i) Determine the oxidation number of sulphur in Na\(_2\)S\(_2\)O\(_3\)

(ii) Name the allotropes of sulphur.

(iii) State two ways in which the structure of graphite and diamond are similar.

(b)(i) Name two green-house gases.

(ii) State one effect of an increased level of green-house gases on the environment.

(iii) State one source from which nitrogen (I) oxide is released into the environment.

(iv) Write a chemical equation to show the effect of heat on each of the following compounds: I. KNO\(_{3(s)}\) II. AgNO\(_{3(s)}\)

(C)(i)Describe briefly how pure crystals of calcium chloride could be obtained from a solution of calcium chloride

ii) Explain briefly each of the following observations:

I. ammonia gas is highly soluble in water;

II. boiling ploint of chlorine is lower than that of iodine

(d) Consider the reaction represented by the following equation:- 2NaCl + H\(_2\)SO\(_{4(s)}\)  \(\to\) Na\(_2\)SO\(_{4(s)}\) + 2HCl\(_{(g)}\)

Calculate the volume of HCl gas that can be obtained at s.t.p. from 5.85 g of sodium. chloride. [ Na = 23.0, Cl = 35.5, Molar volume of gas at s.t.p. = 22.4 dm\(^3\)]

(a)(i) Name a suitable drying agent for the preparation of carbon (IV) oxide in the laboratory.

(ii) Using one chemical test, distinguish between carbon (II) oxide and carbon (IV) oxide.

(b)(i) Describe briefly how oxygen and nitrogen could be obtained separately from air on an industrial scale

(ii) State how a lighted splint can be used to distinguish between samples of oxygen and nitrogen.

(c)(i) Give one reason why bauxite is usually preferred as the ore for the extraction of aluminium.

(ii). List two main impurities. usually present in bauxite.

(iii) State the function of sodium hydroxide solution in the extraction of aluminium from its ore.

(iv) Explain briefly why it is difficult to extract aluminium by chemical reduction of aluminium oxide

(v) Write an equation for the reaction of aluminium oxide with aqueous sodium hydroxide.

(d) (i) The melting and boiling points of sodium chloride are 801 °C and 141.3 °C respectively. Explain briefly why sodium chloride does not conduct electricity at 25°C but does so between 801 °C and 1413 °C.

(ii) State the reason why sodium metal is stored under paraffin oil in the laboratory.

(e)(i) State what would be observed when aqueous sodium trioxocarbonate(IV) is added to a solution containing iron (III) ions

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

(a) (i) Draw the structures of the isomers of the alkene with molecular formurat C\(_4\)H\(_8\)

(ii) State the class of alkanols to which each of the following compounds belongs:

I. CH\(_3\)C(CH\(_3\))\(_2\)OH;

II. CH\(_3\)CH(CH\(_3\))CH\(_2\)OH;

III. CH\(_3\)CH\(_2\)CH(CH\(_3\))OH.

(b) (i) Write the formulae of the products formed in the following reactions:
I. CH\(_3\)CH\(_2\)COOH \(\frac{K_{(s)}}{}\)

II. CH\(_3\)CH\(_2\)COOH. \(\frac{C_4H_6OH, heat}{Conc.H_2SO_4}\)

III. CH\(_3\)CH\(_2\)CH\(_2\)CH\(_2\)OH \(\frac{H^+/KMnO_4}{(excess)}\)

(ii) Name the major product(s) of each of the reactions in (b)(i).

(c) A gaseous hydrocarbon R of mass 7.0 g occupies a volume of 2.24 dm\(^3\) at s. t.p. If the percentage composition by mass of hydrogen is 14.3, determine its:

(i) empirical formula;

(ii) molecular formula. [ H = 1.00, C = 12.0, Molar volume of gas at s.t.p, = 22.4 dm\(^3\) ]

(d) Define structural isomerism.

(a) Consider the following atoms: \(^R_T\)X; \(^S_T\)X.

(i) State the phenomenon exhibited by the two atoms.

(ii) What is the difference between the atoms?

(iii) Give two examples of elements that exhibit the phenomenon stated in (ai)

(iv) lf T is 17, write the electron configuration of the element

(b)(i) State two differences between metals and-non-metals with respect to their:

I. physical properties;

2. chemical properties.

(ii) Give one example of each for the following compounds:

I. an amphoteric oxide;

II. a hydride which evolves hydrogen when reacted with water;

Ill. a trioxocarbonate (IV) salt which is readily decomposed on heating;

IV. a chloride salt which is readily hydrolyzed in water.

(c)(i) State three characteristic properties of transition metals. 

(ii) Write the electron configuration of \(_{30}Zn\)

(iii.) Explain briefly why zinc is not considered as a typical transition element.

(d) Consider the reaction represented by the following equation:- Na\(_2\)CO\(_{3(aq)}\) + MgCl\(_{2(aq)}\) —-> 2NaCl\(_{(aq)}\) + MgCO\(_{3(aq)}\). Calculate the mass of sodium trioxocarbonate (IV) needed to produce 3.36 of magnesium trioxocarbonate (IV). [C = 12.0, O = 16.0, Na = 23.0, Mg = 24:0 ]

(a) What are nucleons?

(b) State Graham’s law of diffusion.

(c) Explain briefly why aluminium does not corrode easily.

(d) State three examples of periodic properties.

(e) State two reasons why real gases deviate from ideal gas behaviour.

(f) List three uses of fractional distillation in industry.

(g) What factors determine the selective discharge of ions at the electrodes during electrolysis?

(h) State the type of reaction represented by each of the following equations:

(i) C\(_2\)H\(_6\) + Br\(_2\) —> C\(_2\)H\(_5\)Br + HBr;

(ii) C\(_2\)H\(_4\) + .Br\(_2\) —> CH\(_4\)Br\(_2\)

(i) Name the products formed when butane burns in limited supply of air.

(j) List three methods of separating a solid from a liquid.

The alkanol obtained from the production of soap is

Which of the following metals is common to both brass and bronze?

A consequences of global warming is

Which of the following sources of energy contributes to green-house effect?

Consider the following reaction equation
C₂H_4(g) + 3O_2(g) \(\to\) 2CO_2(g) + 2H₂O_(l).

The volume of oxygen at s.t.p that will be required to burn 14g of ethene is
[C₂H₄ = 28; Molar volume of gas at s.t.p = 22.4dm³

Which of the following compounds is/are secondary alkanols?

i) CH₃CH(CH₃)CH₃OH
ii) CH₃CH₂CH(OH)CH₃
iii) CH₃C(OH)(CH₃)CH₃

The compound that makes palm wine taste sour after exposure to the air for few days is

Ripening of fruits is hastened by using

When a compound X is heated with concentrated tetraoxosulphate(VI)acid, it produces an alkene. X is an

Amino acids are obtained from proteins by

Consider the following half-cell reactions.
Al_(s) \(\to\) Al³⁺_(aq) + 3e^–
Cu²⁺_(aq) + 2e^– \(\to\) Cu_(s)

The overall equation for the reaction is

Consider the following ionic equation:
Cr₂O₇^2- + 14H⁺ + ne^– \(\to\) 2Cr³⁺ + 7H₂O.
The value of n in the equation is_______?

The oxidation number of sulphur is +4 in