(a)(i) Distinguish between a strong acid and a concentrated acid. (ii) What is meant by...

CHEMISTRY
WAEC 1993

(a)(i) Distinguish between a strong acid and a concentrated acid.

(ii) What is meant by amphoteric oxide? Give one example.

(b)(i) Describe the manufacture of tetraoxosulphate (VI) acid by contact process.

(ii) Write one equation each to show the action of tetraoxosulphate (VI) acid respectively as a dehydrating agent and as an oxidizing agent.

(iii) Give the reason why tetraoxosulphate classified as a heavy chemical.

Explanation

(a) (i) Strong acid can ionize completely E.g. HCI\(_{(aq)}\) —> H\(^{+}_{(aq)}\) + CI\(^-_{(aq)}\) Concentrated acid means great amount of the acidic compound dissolved in little amount of water.

(ii) Amphoteric oxide is a metallic oxide which is both acidic and basic. E.g Al\(_2\)O\(_3\) + 6HCl —> 2AICl\(_3\) + 3H\(_2\)O\(_{(l)}\)

Al\(_2\)O\(_{3(5)}\) + 2NaO\(_{(aq)}\) + 3H\(_2\)O\(_1\) ---> 2NaAl(OH)\(_{4(aq)}\)

(b)(i) The manufacture of H\(_2\)SO\(_4\) by contact process sulphur(VI) oxide, the anhydride of H\(_2\)SO\(_4\) can be obtained by contact process which entails

The sulphur(VI) To dissolved in concentrated H\(_2\)SO\(_4\) to form, a fuming liquid called oleurn (H\(_2\)S\(_2\)O\(_{7(aq)}\))

H\(_2\)SO\(_{4(aq)}\) + SO\(_{3(g)}\) \(\to\) (H\(_2\)S\(_2\)O\(_{7(aq)}\)

The oleum is carefully diluted with correct amount of water to .give ordinary concentrated

H\(_2\)SO\(_{4}\).H\(_2\)S\(_2\)O\(_{7(aq)}\) + H\(_2\)O\(_{(l)}\) --> 2H\(_2\)SO\(_{4(aq)}\)

(ii) H\(_2\)SO\(_4\) as an oxidizing agent C\(_{(S)}\) + 2H\(_2\)SO\(_{4(aq)}\) -->2H\(_2\)O\(_{(l)}\) + 2SO\(_{2(g)}\) + CO\(_{2(s)}\) H\(_2\)SO\(_4\) as a dehydration agent H\(_2\)C\(_2\)O\(_{4(g)}\) + H\(_2\)SO\(_{4(l)}\) --> CO\(_{(g)}\) + CO\(_{2(g)}\) + (H\(_2\)O + H\(_2\)SO\(_{4(aq)}\)

(iii) It is commonly used in most industries.



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