# 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

**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 ?

**Answer:**

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

**Answer:**

**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

**Answer:**

Kelvin zero or absolute zero = — 273°C.

**Question 1.(1992)**

**
**A fixed volume of a gas occupies 760cm

^{3}at 27° C and 70cm of Hg. What will be its vol. at s.t.p. [637 cm

^{3}]

**Answer:**

**Question 1.(1993)**

**State :** Boyle’s Law

**Answer:**

**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 cm

^{3}. 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.

**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 cm

^{3}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

**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.

**Answer:**

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.

**Answer:**

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

**Answer:**

Gas equation.

**Question 4.**

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

**Answer:**

76 cm.

**Question 5.**

**
**The absolute temperature value corresponding to 35°C.

**Answer:**

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.

**Answer:**

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.

**Answer:**

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.

**Answer:**

**Question 4.**

**
**All temperatures on the Kelvin scale are in positive figures.

**Answer:**

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.

**Answer:**

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.

**Answer:**

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