[3 Mark Question Answer]

Question 13 Marks

How is hydrogen separated from carbon dioxide and carbon monoxide?

Answer

$(i)$ The products are hydrogen, carbon dioxide and some
unreacted carbon monoxide. Hydrogen is separated from carbon dioxide by passing the mixture through water under pressure, in which carbon dioxide gets dissolved leaving behind hydrogen. Carbon dioxide can also be separated by passing it through caustic potash $(\mathrm{KOH})$ solution.
$2 \mathrm{KOH}+\mathrm{CO}_2 \longrightarrow \mathrm{K}_2 \mathrm{CO}_3{ }^{+} \mathrm{H}_2 \mathrm{O}$
$(ii)$ To separate carbon monoxide the gaseous mixture is passed through ammoniacal cuprous chloride in which carbon monoxide dissolves leaving behind hydrogen.

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Question 23 Marks

Give equations for the reactions.

Answer

$(i)$ Steam is passed over hot coke at $1000^{\circ} \mathrm{C}$ in a furnace called converters. As a result water gas is produced which is a mixture of carbon monoxide and hydrogen gases.
$\underset{\text { hot coke }}{\mathrm{C}}+\underset{\text { steam }}{\mathrm{H}_2 \mathrm{O}} \xrightarrow{1000^{\circ} \mathrm{C}}\left(\underset{\text { water gas }}{\mathrm{CO}+\mathrm{H}_2}\right)-$Heat
$(ii)$ Water gas is mixed with excess of steam and passed over a catalyst ferric oxide $\left(\mathrm{Fe}_2 \mathrm{O}_3\right)$ and a promotor chromium trioxide $\left(\mathrm{Cr}_2 \mathrm{O}_3\right)$.
$\left.\underset{\text { water gas }}{\left(\mathrm{CO}+\mathrm{H}_2\right)}\right.+\underset{\text { steam }}{\mathrm{H}_2 \mathrm{O}} \xrightarrow[450^{\circ} \mathrm{C}]{\mathrm{FeO}_2 / \mathrm{Cr}_2 \mathrm{O}_3} \mathrm{CO}_2+2 \mathrm{H}_2+$ Heat

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Question 33 Marks

Hydrogen is a good reducing agent: What do you understand by the above statement? Explain with the help of copper oxide as an example.

Answer

Hydrogen acts as a good reducing agent means, when hydrogen gas is passed over hot metallic oxides of copper, lead, iron, etc. it removes oxygen from them and thus reduces them to their corresponding metal.
Let us consider the following example, in each of which metallic oxide react with hydrogen. Metallic oxide act as oxidising agents and hydrogen acts as a reducing agents.

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Question 43 Marks

How would you show that hydrogen is lighter than air?

Answer

Take a delivery tube and place one of its ends in a soap solution kept in a trough and the other one in a flat bottom jar as shown in the figure. The soap bubbles containing hydrogen rise upward the air. The rising soap bubbles prove that hydrogen is lighter than air.

Hydrogen$-$filled soap bubbles rising upward in the soap solution and into the air shows that hydrogen is lighter than air.

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Question 53 Marks

How would you show that hydrogen is a non$-$supporter of combustion?

Answer

Hold a hydrogen gas filled jar with its mouth downwards.
Place a lighted candle inside the jar. The candle gets extinguished but the gas bums with a pop sound. This shows that hydrogen is non$-$supporter of combustion.

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Question 63 Marks

Give reasons for the following : Hydrogen can be used as a fuel.

Answer

Because of its high heat of combustion, hydrogen is used as a fuel. Coal gas, water gas $(CO + H_2)$ and liquid hydrogen are some significant hydrogen$-$based fuels. Liquid hydrogen is used as a rocket fuel. Hydrogen can become the mass fuel of the future, replacing the hydrocarbons. In addition, hydrogen is a pollution$-$free fuel.

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Question 73 Marks

State four uses of hydrogen:

Answer

$1.$ Hydrogen with oxygen produce oxy$-$hydrogen flame which is used for cutting and welding.
$2.$ Hydrogen gas is used as a fuel.
$3.$ Hydrogen is used for hydrogenation of vegetable oil.
$4.$ Hydrogen gas is used extensively in the manufacture of ammonia gas, which is used to produce fertilizers.

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