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3546

(a) Give one example of a metal which:

(i) can displace hydrogen from cold water

(ii) at red-heat, reacts reversibly with steam

(iii) does not react with dilute hydrochloric acid

 

(b) When dry hydrogen was passed over lead (II) oxide, a greyish solid J was obtained.

(i) Identify J

(ii) What type of reaction was involved in the formation of J from lead (II) oxide?

View Answer & Discuss (1) WAEC 1997
3547

(a)(i) Define entropy

(ii) What term is used to describe a reaction in which heat is absorbed from the surrounding?

(b) State two conditions that can lead to ineffective collisions during a chemical reaction.

View Answer & Discuss WAEC 1997
3548

(a)(i) List two reactants for the laboratory preparation of ammonia

(ii) State three physical properties of ammonia

(iii) Describe in outline, the manufacture of ammonia by the Haber process.

 

(b) Write an equation in each case to show the:

(i) reaction between ammonia gas and heated copper (II) oxide

(ii) action of heat on ammonium trioxocarbonate (IV)

 

(c)(i) Which industrial process is used for convey ammonia to trioxonitrate (V) acid?

(ii) Give the reason why electropositive metals do not generally are off hydrogen with dilute trioxonitrate (V) acid

(d) Give one example in each case, to show how trioxonitrate (V) acid reacts generally with: (i) bases (ii) non-metals.

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3549

(a)(i) State two general methods of preparing soluble salts.

(ii) Mention three pieces of apparatus required for determining the solubility of a salt at a given temperature.

 

(b) The solubilities of two salts represented as K and L were determined at various temperatures. The results are shown in the table below:

Temperature (\(^o\)C) 0 20 40 60 80 90
Solubility of K (mol. dm\(^{-3}\)) 0.38 0.46 0.54 0.62 0.69 0.73
Solubility of L (mol. dm\(^{-3}\)) 0.12 0.34 0.64 1.08 1.64 2.00

 

(i) Plot the solubility curves of K and L on the same graph. Use the curves to answer questions (ii) - (iv) below.

(ii) What is the solubility of K at 50°C?

(iii) At what temperature is the solubility of L equal to 1.0mol. dm\(^{-3}\)?

(iv) Over what temperature range is K more soluble that L?

(v) Given that the molar mass of L is 101g, determine whether a solution containing 3.4g of L per 250cm\(^3\) at 20°C is saturated or unsaturated.

View Answer & Discuss WAEC 1997
3550

(a)(i) What is meant by cracking of petroleum fractions?

(ii) Write an equation for the laboratory preparation of ethene from ethanol.

(iii) Give one chemical test to distinguish between ethane and ethene.

 

(b)(i) Name the class of carbohydrates to which starch and cellulose belong.

(ii) What process is used for isolating ethanol from the other products of fermentation of sugar?

(iii) Name the organic product of the reaction between ethanol and sodium

(iv). Write the structural formula of 2-chloroethanol.

 

(c) State the reason why:

(i) benzene produces more soot than ethene on burning in excess air;

(ii) ethanoic acid has a higher boiling point than methanoic acid;

(iii) sodium chloride is used during the manufacture of soap.

(d) Give one use of: (i) ethyne (ii) coal (iii) carbon black

View Answer & Discuss WAEC 1997
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