[2 Mark Question Answer]

Question 12 Marks

By giving examples explain the following terms:
(a) Oxidation reaction
(b) Reduction reaction

Answer

(a) Oxidation reaction is a chemical reaction in which oxygen is added to or hydrogen is removed from an element, molecule or a compound
(b) A reduction reaction is a chemical reaction in which oxygen is removed or hydrogen is added to an element, molecule, or compound.

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Question 22 Marks

How is hydrogen prepared industrially by Bosch Process?

Answer

Preparation of hydrogen by Bosch’s process Industrially, hydrogen is prepared by passing steam over red-hot coke at high temperature. The products are CO and hydrogen. This mixture of carbon monoxide and hydrogen is called is called water gas

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Question 32 Marks

(a) why does hydrogen gas collected from zinc has a characteristic fishy smell?
(b) Name the chemicals used in the purification of hydrogen gas prepared from granulated zinc.

Answer

(a) Granulated zinc contains traces of zinc phosphide. The zinc phosphide reacts with dilute sulphuric acid to liberate phosphine gas, which has a fishy smell.
(b) Silver nitrate solution(AgNO₃), lead nitrate solution [Pb(NO₃)₂], potassium hydroxide solution (KOH) and anhydrous calcium chloride (CaCl₂) solutions are used in the purification of hydrogen gas prepared from granulated zinc

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Question 42 Marks

How will you prepare hydrogen gas in laboratory’? State three precautions necessary for the collection of hydrogen.

Answer

Hydrogen is prepared in the laboratory by the action of the dilute hydrochloric acid or dilute sulphuric acid on granulated zinc. Granulated zinc gives more surface area for the acid to act, so hydrogen is formed faster

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Question 52 Marks

(a) Name two metals which react with cold water to form hydrogen. Write the balanced chemical equations.
(b) Name two metals which react with steam and displace hydrogen. Write the balanced chemical equations.

Answer

(a) sodium and potassium .
$
\begin{aligned}
& 2 \mathrm{~K}+2 \mathrm{H} 2 \mathrm{O} \rightarrow 2 \mathrm{KOH}+\mathrm{H}_2 \\
& 2 \mathrm{Na}+2 \mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{NaOH}+\mathrm{H}_2
\end{aligned}
$

(b) Magnesium, Aluminum
$
\begin{aligned}
& \mathrm{Mg}+\mathrm{H} 2 \mathrm{O} \rightarrow \mathrm{MgO}+\mathrm{H}_2 \\
& 2 \mathrm{Al}+3 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Al} 2 \mathrm{O} 3+\mathrm{H}_2
\end{aligned}
$

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CHEMISTRY [2 Mark Question Answer]

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