Class 10 Gases Exercise 16.1 Solutions | Science and Technology Curriculum Development Centre

Carbon dioxide (\(\rm CO_{2}\)) can be collected in an open gas jar because it is denser than air(1.5 times heavier than air).

When \(\rm CO_{2}\) is released into the jar, it sinks to the bottom and displaces the lighter air above it. This property allows it to be collected by upward displacement of air, without the gas quickly escaping, making it easy to gather in an open container.

The bottle of liquid ammonia (\(\rm NH_{3}\)) should be placed in cold water or ice before opening its lid because ammonia has a low boiling point of about -33 °C (-27 °F). 

When the bottle is opened, ammonia can rapidly vaporize, leading to a significant drop in temperature and the potential for the liquid ammonia to boil violently. Placing the bottle in cold water or ice helps to cool the ammonia further, reducing the pressure inside the bottle and minimizing the risk of a sudden release of gas, which can be hazardous. This precaution ensures safer handling of ammonia by preventing splashing or excessive gas release upon opening.

1.Ans:

From the figure,

Carbon dioxide (\(\rm CO_{2}\)) is being collected in the gas jar.

2.Ans:

The balanced chemical reaction for preparation of this gas is:

\(\rm CaCO_{3} \) + \(\rm 2HCl \) → \(\rm CaCl_{2} \) + \(\rm H_{2}O \) + \(\rm CO_{2}\)

3.Ans:

Carbon dioxide is acidic in nature.

Hence, a wet blue litmus paper is used to identify carbon dioxide. It turns into red.

4.Ans:

Carbon dioxide is 1.5 times heavier than air.

So, it will not escape from the gas jar kept straight upright. Hence, this gas collected in the gas jar kept straight upright.

Any three properties of carbon dioxide gas are:

1. Carbon dioxide is a colorless and odorless gas with a faint acidic taste.
2. It is 1.5 times heavier than air, so it is present in deep wells, mines, etc. Moreover, it can also be poured from one vessel to another.
3. It is acidic in nature, so it turns blue litmus into red.

Any four uses of carbon dioxide gas are:

1.  Carbon dioxide is used in the manufacture of soft drinks.
2. It is used for extinguishing fire.
3. Carbon dioxide is used to manufacture sodium carbonate by ammonia-soda method.
4. It is used for the manufacture of urea (carbamide), a chemical fertilizer.

Laboratory Preparation of Ammonia gas:

Principle: When finally crushed mixture of dry solid Ammonium Chloride and Calcium Hydroxide (slaked lime) is heated in the ratio of 2:1, the react with each other to release Ammonia gas

\(\rm 2NH_{4}Cl\) + \(\rm Ca(OH)_{2}\) → \(\rm CaCl_{2}\) + \(\rm 2H_{2}O\) + \(\rm 2NH_{3}\)

Requirements:

Apparatus: hard glass test tube, a spirit lamp, a bunsen burner, a delivery tube, a lime tower, a gas jar, corks,  stand and clamp

Chemicals: ammonium chloride(\(\rm NH_{4}Cl\)), calcium hydroxide [\(\rm Ca(OH)_{2}\)]

Procedure

1. A mixture of ammonium Chloride and slaked lime(2:1) is taken in a hard glass test tube.

2. The hard glass test tube is clamped on a stand in an inclined position.

3. A delivery tube is fitted in a cork that is adjusted in the test tube.

4. The free end of the delivery tube is taken in a lime tower filled with quicklime. The quick lime absorbs the moisture.

5. Now the delivery tube is taken in an inverted dry gas are as shown in the figure. Then the test tube is heated gently.

On heating the mixture, ammonia is released from the mixture. The formed materials are passed into the lime tower containing quicklime. The lime tower is used to obtain dry ammonia. The released ammonia is collected by the downward displacement of air in the jar.

Precautions:

1. The apparatus must be made airtight.
2. The hard glass tube should be fixed in an inclined position towards its mouth in order to prevent it from cracking.
3. Heat should be provided uniformly.
4. The gas jar should be dried.

1.Ans:

Given diagram is of laboratory preparation of ammonia gas.

Ammonia (\(\rm NH_{3}\)) is being collected in the gas jar.

2.Ans:

The balanced chemical equation for the preparation of this gas is:

\(\rm 2NH_{4}Cl\) + \(\rm Ca(OH)_{2}\) → \(\rm CaCl_{2}\) + \(\rm 2H_{2}O\) + \(\rm 2NH_{3}\)

3.Ans:

Ammonia is basic in nature.

So, A moist red litmus is used to identify the gas. When it is inserted in the jar containing ammonia gas, it turns blue.

4.Ans:

The hard glass tube should be fixed in an inclined position towards its mouth in order to prevent it from cracking.

5.Ans:

The product from the shown experiment should be passe through a lime tower before its collection in the gas jar to absorb its moisture. 

Any four uses of ammonia gas are:

1. It is used to prepare urea.
2. It is used to prepare nitric acid by Ostwald’s process.
3. Its solution is used as a laboratory reagent.
4. It is used for developing blueprints of maps.

1.Ans:

When carbon dioxide is passed intro lime water for a short period of time, the lime water turns milky. This is due to formation of insoluble calcium carbonate.

\(\rm Ca(OH)_{2}\) + \(\rm CO_{2}\) → \(\rm CaCO_{3} \)(milky) + \(\rm H_{2}O\)

2. Ans:

If \(\rm CO_{2}\) is passed in lime water continuously for a long period of time, the formed milky colored insoluble calcium carbonate disappears slowly due to the formation of soluble calcium bicarbonate \(\rm [Ca(HCO_{3})_{2}] \).

\(\rm CaCO_{3} \) + \(\rm CO_{2}\) + \(\rm H_{2}O\) → \(\rm Ca(HCO_{3})_{2} \)

3.Ans:

When burning magnesium is inserted into a jar containing carbon dioxide, it burns continuously and forms magnesium oxide (white) and carbon ( black).

\(\rm 2Mg\) + \(\rm CO_{2}\) → \(\rm 2MgO\) + \(\rm C\)

1.Ans: 

When a finely crushed mixture of dry solid ammonium chloride and calcium hydroxide is heated in the ratio of 2:1, they react with each other to release ammonia gas.

\(\rm 2NH_{4}Cl \)+\(\rm Ca(OH)_{2} \) → \(\rm CaCl_{2} \) + \(\rm 2H_{2}O\)+\(\rm 2NH_{3} \)

2.Ans:

Ammonia dissolves in water easily to give a solution called ammonium hydroxide.

\(\rm NH_{3} \) + \(\rm H_{2}O\) → \(\rm NH_{4}OH \)

3.Ans:

Ammonia reacts with hydrochloric acid to give ammonium chloride salt.

\(\rm NH_{3} \) + \(\rm HCl\) → \(\rm NH_{4}Cl\)