Explain Statement.

Question 11 Mark

Production of water gas:

Answer

$\begin{aligned} & C + H _2 O \longrightarrow CO \uparrow+ H _2 \uparrow \\ & \begin{array}{ll:l}\text { Red hot } & \begin{array}{l}\text { Super heated } \\ \text { coke }\end{array} \text { steam } & \begin{array}{l}\text { Carbon } \\ \text { monoxide }\end{array}\end{array} \\ & \end{aligned}$
When super heated steam is passed over red hot coke at high temperature, it forms carbon monoxide gas and hydrogen gas.
This gaseous product of carbon monoxide gas and hydrogen gas together is called as water gas.

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Question 21 Mark

Production of methane gas in biogas plant.

Answer

$\begin{aligned} & CH _3 COOH \longrightarrow CH _4+ CO _2 \uparrow \\ & \text { Organic acid Methane Carbon } \\ & \text { (Acetic acid) dioxide } \\ & \end{aligned}$

In biogas plant, microbes act on the bio-degradable complex organic compounds and produce organic acids.

The methanogenic bacteria act on the organic acids to produce Methane gas and Carbon dioxide gas.

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Question 31 Mark

Methane and Chlorine gases react with each other.

Answer

$\begin{aligned} & CH _4+ Cl _2 \stackrel{\text { Light }}{\longrightarrow} CH _3 Cl + HCl \\ & \text { Methane Chlorine Methyl Hydrogen } \\ & \text { Chloride Chloride } \\ & \end{aligned}$

Methane and chlorine gases react with each other at the temperature of 250 °C to 400 °C in presence of ultra voilet light and form mainly Methyl chloride (Chloromethane and ‘ Hydrogen chloride)
This reaction is called Chlorination of methane.

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Question 41 Mark

Methane gas is burnt in air:

Answer

$\underset{\text { Methane }}{ CH _4}+\underset{\text { Oxygen }}{2 O _2} \longrightarrow \underset{\text { Carbon } \text { dioxide }}{ CO _2 \uparrow} + \underset{\text { Water }}{2 H _2 O } +$
heat Methane is highly inflammable, it burns in air with a bluish flame and combines with oxygen present in air to form Carbon dioxide and water. In these reaction $213 \ \ce{kcal/mol}$ of heat is given out.

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Question 51 Mark

Sodium bicarbonate reacts with dilute Sulphuric acid, $($reaction in fire extinguisher$):$

Answer

$\begin{aligned} & \ce{2NaHCO_3 + H_2SO_4} \rightarrow \ce{Na_2SO_4 + 2 H_2O + 2CO_2} \uparrow \\ & \begin{array}{lllll}\begin{array}{l}\text { Sodium } \\ \text { bicarbonate }\end{array} & \begin{array}{l}\text { Sulphuric } \\ \text { acid }\end{array} & \begin{array}{l}\text { Sodium } \\ \text { sulphate }\end{array} & \text { Water } & \begin{array}{l}\text { Carbon } \\ \text { dioxide }\end{array}\end{array} \\ & \end{aligned}$
When Sodium bicarbonate reacts with dilute Sulphuric acid it forms Sodium sulphate, water and Carbon dioxide gas.

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Question 61 Mark

Carbon dioxide gas is dissolved in water.

Answer

$\begin{aligned} & CO _{2( g )}+ H _2 O \longrightarrow H _2 CO _3 \\ & \text { Carbon Water Carbonic } \\ & \text { dioxide } \quad \text { acid } \\ & \end{aligned}$Carboh dioxide gas is fairly soluble in water, it dissolves in water under pressure to form Carbonic acid.

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Question 71 Mark

Carbon dioxide is passed through freshly prepared lime water for a short duration and then for longer duration:

Answer

$\begin{aligned} & \ce{Ca(OH)_2 + CO_2} \longrightarrow \ce{H_2O + CaCO_3} \downarrow \\ & \begin{array}{llll}\text { Calcium } & \begin{array}{l}\text { Carbon } \\ \text { hydroxide }\end{array} & \text { Water } & \begin{array}{l}\text { Calcium } \\ \text { carbonate }\end{array}\end{array} \\ & \text { (lime water) _ (white) } \\ & \end{aligned}$
When Carbon dioxide is passed through freshly prepared lime water, it forms water and white precipitate of Calcium carbonate because of which lime water turns milky.

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Question 81 Mark

Carbon dioxide is passed through an aqueous solution of Sodium carbonate:

Answer

$\begin{aligned} & \ce{Na_2CO_3 + H_2O + CO_2} \longrightarrow \ce{2NaHCO_3} \\ & \begin{array}{llll}\begin{array}{l}\text { Sodium } \\ \text { carbonate }\end{array} & \text { Water } & \begin{array}{l}\text { Carbon } \\ \text { dioxide }\end{array} & \begin{array}{l}\text { Sodium } \\ \text { bicarbonate }\end{array}\end{array} \\ & \end{aligned}$

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Question 91 Mark

Carbon dioxide is passed through an aqueous solution of Sodium hydroxide:

Answer

$\begin{aligned} & 2 NaOH + CO _2 \longrightarrow Na _2 CO _3+ H _2 O \\ & \text { Aqueous Carbon Sodium Water } \\ & \text { Sodium dioxide carbonate } \\ & \text { hydroxide } \\ & \end{aligned}$

When Carbon dioxide gas is passed through an aqueous solution of Sodium hydroxide it forms Sodium carbonate and Water

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Question 101 Mark

Calcium carbonate reacts with dilute hydrochloric acid:

Answer

$\begin{aligned} & \text { acid } \\ & \end{aligned}$

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Question 111 Mark

Coal when burnt in air

Answer

$C \quad+ O _2 \longrightarrow CO _2 \uparrow$

When coal is burnt in air, the carbon present in coal combines with oxygen present in air to form carbon dioxide gas.

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Question 121 Mark

Preparation of urea from Ammonium cyanate:

Answer

$\begin{aligned} & NH _4^{+} CNO ^{-} \stackrel{\text { Heat }}{\longrightarrow} NH _2 CONH _2 \\ & \text { Ammonium } \\ & \text { Urea } \\ & \text { Cyanate } \\ & \end{aligned}$

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