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Chemistry [5 Mark Question Answer]

9.1 Ammonia · ICSE STD 10 (ICSE - English Medium). 11 questions.

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[5 Mark Question Answer]

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Question 15 Marks
The diagram shows an experimental set-up for the laboratory prepration of a pungent smelling gas. The gas is alkaline in nature.

(i) Nature the gas collected in the jar.(ii) Write the balance equation for the above preparation.(iii) How is the gas being collected?(iv) Name the drying agent used.(v) How will you find that the jar is full of gas?
Answer
(i) Ammonia
(ii)$
2 NH _4 CI + Ca ( OH )_2 \xrightarrow{\text { Heat }} CaCI _2+2 H _2 O +2 NH _3 \uparrow
$
(iii) By downward displacement of air
(iv) Quicklime/CaO
(v) Bring moist red litmus paper to the mouth of the inverted jar; it immediately turns blue.
Or
Bring a glass rod dipped in hydrochloric acid to the
mouth of the inverted jar. If it produces dense white
fumes, then the jar is full of gas.
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Question 25 Marks
The diagram shows a simple arrangement of the fountain experiment:
Image
(i) Name the two gases you have studied which can be used in this experiment(ii) What is the common properly demonstrated by this experiment
Answer
(i) Ammonia and hydrogen chloride gas
(ii) High solubility of gases in water
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Question 35 Marks
The questions below are related to the manufacture of ammonia. (i) Name the process (ii) In what ratio must the reactants be taken (iii) Name the catalyst used (iv) Give the equation for the manufacture of ammonia (v) Ammonia can act as a reducing agent write a relevant equation for such a reaction.
Answer
(i) Habers process (ii) 1 part of nitrogen and 3 parts of hydrogen (iii) Finely divided iron (Fe) (iv) (v)
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Question 45 Marks
Give one use each of four different compounds of ammonia.
Answer
(i) Use of Ammonium Chloride
Used in Leclanche cell and dry cell
(ii) Use of Ammonium Sulphate
Used as a fertilizer
(iii)use of Ammonium nitrate
Used in fireworks
(i) Use of Ammonium Carbonate
Used in baking powder
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Question 55 Marks
How is an aqueous solution of ammonia prepared? Stage two advantages of method used.
Answer
An aqueous solution of ammonia is prepared by dissolving ammonia in water. Ammonia is highly soluble in water.

The funnel arrangement is used to prepare aqueous solution of ammonia. In this method, ammonia gas is introduced through a funnel tube where the rate of dissolution of ammonia is faster than it is produced. This creates a partial vacuum, in delivery tube, resulting in low pressure. Thus, water is forced in to equalise the pressure. To overcome this problem of back suction, the funnel is attached to outer end of the delivery tube and mouth of funnel just dips into the water in the trough.
Two advantages of this method :
(i) Prevents back suction of water into the fla sk.
(ii ) Provides a larger surface area for the absorption of the gas.
Key: Ammonia is highly soluble in water.
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Question 65 Marks
Draw the structure of ammonia and give the reason for alkaline nature of aqueous ammonia.
Answer


The presence of lone pair of electrons on the nitrogen atom makes ammonia basic in nature in its aqueous solution. Aqueous solution of ammonia dissociates partially to produce hydroxylion.
$
\begin{aligned}
& Nh _3+ H _2 O \rightleftharpoons NH _4 OH \\
& NH _4 OH \rightleftharpoons NH _4^{+}+ OH ^{-}
\end{aligned}
$
Key: Aqueous solution of ammonia is alkaline in nature.
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Question 75 Marks
Give three reactions to show reducing property of ammonia.
Answer
Ammonia is a strong reducing agent. It is oxidised to nitrogen by removal of hydrogen, when it react with oxidizing agent.
(i) Reduction of chlorine
$
8 NH _3 \text { (excess) }+3 CI _2 \longrightarrow N _2+6 NH _4 CI
$
(ii) Reduction of copper (II) oxide
$
3 CuO +2 NH _3 \xrightarrow{\Delta} 3 Cu +3 H _2 O + N _2
$
Black Reddish brown
(iii) Reduction of lead (II) oxide
$
3 PbO +2 Nh _3 \xrightarrow{\Delta} 3 Pb +3 H _2 O + N _2
$
Yellow Grey
Key: Ammonia is a strong reducing agent.
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Question 85 Marks
Why is ammonium hydroxide used in qualitative analysis? Give two equations to justify your answer.
Answer
Ammonium hydroxide precipitates hydroxides of metals when it is added to aqueous solution of their salts. The precipitate of metal hydroxides differ in colour and solubility and hence ammonium hydroxide is used in qualitative analysis.
(i) $FeSO_4 +2NH_4OH \rightarrow (NH_4)_2SO_4 +Fe(OH)_3$
The colour of precipitate is dirty green, which is insoluble in excess of
ammonium hydroxide.
(ii) $CuSO_4 + 2NH_4OH \rightarrow (NH_4)2SO_4 + Cu (OH)_2$​​​​​​​
The colour of precipitate is bluish white, which is soluble in excess of ammonium hydroxide.
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Question 95 Marks
List the properties of ammonia that make it
(i) A good refrigerant
(ii) A cleaning agent
(iii) As a source of hydrogen
Answer
(i) Liquid ammonia is used as refrigerant as:
(a) It is highly volatile
(b) It has high specific latent heat of vaporization. 1 mole (17g) of liquid ammonia vaporises by absorbing 5.7 kcals of heat from the surroundings, which is there by cooled.
(c) It easily liquefies under pressure at room temperature.
(ii) Ammonia emulsifies fats and grease. Thus it is used to clean oils, fats and body grease etc. from clothes.
(iii) Liquid hydrogen is dangerous to transport as it is highly combustible. Thus, hydrogen is converted to liquid ammonia and transported in cylinders. Later it is catalytically converted to hydrogen.
Key: Uses of ammonia
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Question 105 Marks
How will you demonstrate the solubility of ammonia in water? Explain.
Answer
Ammonia is highly soluble in water. This can be demonstrated by Fountain
experiment.
• We take a round bottom flask filled with ammonia gas.
• The flask is closed with a two holed rubber stopper, one for the jet tube and the other for a dropper filled with water.
• The flask is fixed to the stand in an inverted position .
• The free end of the jet tube is dipped into a beaker containing red litmus
solution .
• When the bulb of dropper is pressed, it is observed that red litmus solution rises up and strikes the wall of the flask and spreads in form of fountain, which is blue in colour.
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Question 115 Marks
Name the substance used for drying ammonia gas? Why cannot substances such as conc.$H_2SO_4$​​​​​​​, anhydrous calcium chloride and phosphorus pentoxide be used for drying ammonia gas?
Answer
The substance used for drying ammonia gas is quicklime( calciumoxide) .
Concentrated sulphuric acid, anhydrous calcium chloride and phosphorus pentoxide cannot be used for drying ammonia gas because ammonia being basic reacts wi th them, and the following reaction takes place
Conc.$H_2SO_4$ reacts with ammonia to form ammonium sulphate.
$2 NH_3 + H_2SO_4(conc..) \rightarrow (NH_4)_2SO_4$​​​​​​​
Phosphorus pentoxide reacts with ammonia to form ammonium phosphate.
$6 Nh_3 + P_2O_5 + 3H_2O \rightarrow 2(NH_4)_3PO_4$​​​​​​​​​​​​​​
Anhydrous calcium chloride combines with ammonia to form addi tion compound.
$4 NH_3 + CaCI_2  \rightarrow CaCI_2. 4NH_3$​​​​​​​​​​​​​​
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