Gas Laws Dalal Simplified Class-9 ICSE Chemistry Solutions Chapter-7. Study of Gas Laws by Dr Viraf J Dalal Middle School Chemistry Allied Publishers Answer. We Provide Step by Step Solutions of Exercise/Lesson -7 Study of Gas Laws with Additional Questions , Previous Year Questions and Unit Test-7 of Dr Viraf J Dalal Middle School Chemistry Allied Publishers New Simplified Chemistry . Visit official Website CISCE for detail information about ICSE Board Class-9.

## Study of Gas Laws Dalal Simplified Class-9 ICSE Chemistry Solutions Chapter-7

–: Select Topics :–

### Previous Year Question for Study of Gas Laws

#### Question 1.(1988)

“When stating the volume of a gas the pressure and temperature should also be given”. Why ?
Volume of a gas under goes significant change if its pressure or temperature is slightly changed.

#### Question 1.(1989)

##### Define or state : Boyle’s Law

Boyle’s Law : “Temperature remaining constant the volume of a given mass of dry gas is inversely proportional to its pressure.”

#### Question 2.(1989)

Express Kelvin Zero in °C
Kelvin zero or absolute zero = — 273°C.

#### Question 1.(1992)

A fixed volume of a gas occupies 760cm3 at 27° C and 70cm of Hg. What will be its vol. at s.t.p. [637 cm3] Answer:

#### Question 1.(1993)

State : Boyle’s Law
Boyle’s Law : “Temperature remaining constant the volume of a given mass of dry gas is inversely proportional to its pressure.”

#### Question 1.(1995)

At 0°C and 760 mm Hg pressure, a gas occupies a volume of 10Q cm3. The Kelvin temperature (Absolute temperature) of the gas is increased by one-fifth while the pressure is increased one and a half times. Calculate the final volume of the gas. [80 cc.] Answer:

#### Question 1.(1996)

The pressure on one mole of gas at s.t.p. is doubled and the temperature is raised to 546 K. What is the final volume of the gas ? [one mole of a gas occupies a volume of 22.4 litres at stp.] [22.4 ltrs.] Answer:

#### Question 1.(1997)

Is it possible to change the temperature and pressure of a fixed mass of gas without changing its volume. Explain your answer.
No, it is not possible as change of any one of the parameters (pressure or temperature) has significant effect on volume.

### Additional Questions Study of Gas Laws by Dr Viraf J Dalal Middle School New Simplified Chemistry Allied Publishers

#### Question 1.

What volume will a gas occupy at 740 mm pressure which at 1480 nun occupies 500 cc ? [Temperature being constant] [1000 cc] Answer:

#### Question 2.

The volume of a given mass of a gas at 27°C is 100 cc. To what temperature should it be heated at the same pressure so that it will occupy a volume of 150 cc ?[177°C] Answer:

#### Question 3.

A fixed mass of a gas has a volume of 750 cc at—23°C and 800 mm pressure. Calculate the pressure for which its volume will be 720 cc. The temperature being —3°C. [900mm] Answer:

#### Question 4.

What temperature would be necessary to double the volume of a gas initially at s.t.p. if the pressure is decreased by 50% ? [0°C] Answer

#### Question 5.

A gas cylinder having a capacity of 20 litres contains a gas at 100 atmos. How many flasks of 200 cm3 capacity can be filled from it at 1 atmos. pressure if the temperature remains constant ? [10,000] Answer:

#### Question 6.

A certain mass of gas occupied 850 ml at a pressure of 760 mm of Hg. On increasing the pressure it was found that the volume of the gas was 75% of its initial value. Assuming constant temperature, find the final pressure of the gas? [1013.33 mm of Hg] Answer:

#### Question 7.

It is required to reduce the volume of a gas by 20% by compressing it at a constant pressure. To do so, the gas has to be cooled. If the gas attains a final temperature of 157°C, find the initial temperature of the gas ? [264.5°C] Answer:

#### Question 8.

At a given temperature the pressure of a gas reduces to 75% of its initial value and the volume increases by 40% of its initial value. Find this temperature if the initial temperature was —10°C. [3.15°C] Answer:

### Unit Test Paper 7 Study Of Gas Laws Dalal Simplified Class-9 ICSE Chemistry Solutions

#### Q.1. Name or state the following :

Question 1.

The law which states that pressure remaining constant the volume of a given mass of dry gas is directly proportional to its absolute [Kelvin] temperature.
Charle’s Law.

#### Question 2.

The law which studies the relationship betweeir pressure of a gas and the volume occupied by it at constant temperature.
Boyle’s Law.

#### Question 3.

An equation used in chemical calculations which gives a simultaneous effect of changes of temperature and pressure on the volume of a given mass of dry gas
Gas equation.

#### Question 4.

The standard pressure of a gas in cm. of mercury corresponding to one atmospheric pressure.
76 cm.

#### Question 5.

The absolute temperature value corresponding to 35°C.
35 + 273 = 308K

### Q.2. Give reasons for the following :(Gas Laws Dalal Simplified )

#### Question 1.

Gases unlike solids and liquids exert pressure in all directions.
Impact of gas molecules with high velocity causes pressure to be exerted on the walls.

#### Question 2.

Gases have lower densities compared to solids or liquids.
Gases have low densities as the inter-molecular distance between the molecules of gases is very large.

#### Question 3.

Temperature remaining constant the product of the vol. & the press, of a given mass of dry gas is a constant.

#### Question 4.

All temperatures on the Kelvin scale are in positive figures.
All temperatures on the Kelvin scale are in positive figures.
The temperature -273°C = OK [Absolute zero or zero Kelvin] Hence it may be negative or positive on Celsius scale, it is always positive on Kelvin as 0°C = 0 + 273 = 273K
30°C = 30 + 273 = 303 K
– 70°C = – 70+ 273;= 203 K
– 273°C = – 273 + 273 = 0K

#### Question 5.

Volumes of gases are converted into s.t.p. conditions and then compared.
Volumes of gases are converted into s.t.p. conditions and then compared as
volumes of gases change with temperature and pressure – hence a standard value of temperature and pressure is chosen to which gas volumes are referred.

### Q.3. Calculate the following : (Gas Laws Dalal Simplified )

#### Question 1.

Calculate the temperature to which a gas must be heated, so that the volume triples without any change in pressure. The gas is originally at 57”C and having a volume 150 cc.

#### Question 2.

A gas ‘X’ at -33°C is heated to 127° C at constant pressure. Calculate the percentage increase in the volume of the gas.

#### Question 3.

Calculate the volume of a gas ‘A’ at s.t.p., if at 37°C and 775 mm of mercury pressure, it occupies a volume of 9 1/2 litres.

#### Question 4.

Calculate the temperature at which a gas ‘A’ at 20°C having a volume, of 500 cc. will occupy a volume of 250 cc.

#### Question 5.

A gas ‘X’ is collected over water at 17°C and 750 mm. pressure. If the volume of the gas collected is 50 cc., calculate the volume of the dry gas at s.t.p. [at 17°C the vapour pressure is 14 mm.] Answer:

### Q.5. Calculate the following : (Gas Laws Dalal Simplified )

#### Question 1.

The temp, at which 500 cc. of a gas ‘X’ at temp. 293K occupies half it’s original volume [pressure constant].

#### Question 2.

The volume at s.t.p. occupied by a gas “Y” originally occupying 760 cc. at 300K and 70 cm. press, of Hg.

#### Question 3.

The volume at s.t.p. occupied by a gas ‘Z’ originally occupying 1.57 dm3 at 310.5K and 75 cm. press. of Hg.

#### Question 4.

The volume at s.t.p. occupied by a gas ‘Q’ originally occupying 153.7 cm3 at 287K and 750 mm. pressure [vapour pressure of gas ‘Q’ at 287K is 12 mm of Hg.] Answer:

#### Question 5.

The temperature to which a gas ‘P’ has to be heated to triple it’s volume, if the gas originally occupied 150 cm3 at 330K [pressure remaining constant].

### Q.6. Fill in the blanks with the correct word, from the words in bracket : (Gas Laws Dalal Simplified )

#### Question 1.

If the temperature of a fixed mass of a gas is kept constant and the pressure is increased, the volume correspondingly ____ [increases / decreases] Answer:
If the temperature of a fixed mass of a gas is kept constant and the pressure is increased, the volume correspondingly decreases.

#### Question 2.

If the pressure of a fixed mass of a gas is kept constant and the temperature is increased, the volume correspondingly ____ [increases / decreases] Answer:
If the pressure of a fixed mass of a gas is kept constant and the temperature is increased, the volume correspondingly increases.

#### Question 3.

1 dm3 of a gas is equal to ____ [1 litre / 100ml. / 100 cc.] Answer:
1 dm3 of a gas is equal to 1 litre.

#### Question 4.

All the temperature on the kelvin scale are in ____ figures [negative positive] Answer:
All the temperature on the kelvin scale are in positive figures.

#### Question 5.

At -273°C the volume of a gas is theoretically ____ [272 cc. / 0 cc. / 274 cc.] Answer:
At -273°C the volume of a gas is theoretically 0 cc.

.– : End of Gas Laws Dalal Simplified Solutions :–

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