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Chemistry WAEC Past Questions

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1286

(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.

View Answer & Discuss WAEC 2016
1287

(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).

View Answer & Discuss WAEC 2016
1288

(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\(^3\)]

View Answer & Discuss WAEC 2016
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1289

(a) (i) Define the term fermentation

(ii) Name the catalyst that can be used for this process

(b) Name two factors which determine the choice of an indicator for an acid-base titration

(c) Consider the following reaction equation: Fe + H\(_2\)SO\(_4\) \(\to\) FeSO\(_4\) + H\(_2\). Calculate the mass of unreacted iron when 5.0g of iron reacts with 10cm\(^3\) of 1.0 moldm\(^3\) H\(_2\)SO\(_4\), [Fe = 56.0]

(d)  Name one:

(i) Heavy chemical used in electrolytic cells

(ii) Fine chemical used in textile industries

(e) Explain briefly how a catalyst increases the rate of a chemical reaction.

(f) (i) Write the chemical formula for the product formed when ethanoic acid reacts with ammonia

(ii) Give the name of the product formed in (f)(i)

(g) List three properties of aluminum that makes it suitable for the manufacture of drinks cans

(h) State two  industrial uses of alkylalkanoates

(i) Name two steps involved in the crystallization of a salt from its solution

(j) List two effects of global warming

View Answer & Discuss (2) WAEC 2018
1290

(a) Define esterification.

(b) State two properties of plastic.

(c) Name the components of duralumin.

(d) What is meant by each of the following terms?

(i) Raw material.

(ii) Primary product.

(e) State Charles' law.

(f) List four pieces of protective equipment in the laboratory.

(g) Give two uses of ammonia.

(h) Name the:

(i) process by which lighter hydrocarbons are obtained from heavier ones;

(ii) products formed from the reaction between ethanol and sodium metal.

(i) Determine the oxidation number of sulphur in H\(_2\)SO\(_4\).

(j) Write the IUPAC name for each of the following compounds: (i) NaClO\(_3\); (ii) CuSO\(_4\)5H\(_2\)O.

View Answer & Discuss WAEC 2015
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