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## Sunday, 21 February 2021

### CBSE Class 11 Chemistry - MCQ and Online Tests - Unit 5 - States of Matter

#### CBSE Class 11 Chemistry – MCQ and Online Tests – Unit 5 – States of Matter

Every year CBSE schools conducts Annual Assessment exams for 6,7,8,9,11th standards. These exams are very competitive to all the students. So our website provides online tests for all the 6,7,8,9,11th standard’s subjects. These tests are also very effective and useful for those who preparing for any competitive exams like Olympiad etc. It can boost their preparation level and confidence level by attempting these chapter wise online tests.

These online tests are based on latest CBSE syllabus. While attempting these our students can identify the weak lessons and continuously practice those lessons for attaining high marks. It also helps to revise the NCERT textbooks thoroughly.

CBSE Class 11 Chemistry – MCQ and Online Tests – Unit 5 – States of Matter

Question 1.
Falling drop of water is spherical due to:
(a) Hydrogen Bonding
(b) Surface Tension
(c) Capillary Action
(d) Vlscosity

Explanation:
Raindrops take up the spherical shape due to the surface tension of water which is caused due to the tendency of water molecules to stick together. The spherical shape is having the least possible surface area due to which it can resist any of the external force in the atmosphere.

Question 2.
The rates of diffusion of gases are inversely proportional to square root of their densities . This statement refers to :
(a) Daltons Law
(b) Grahams Law
(d) None of the Above

Explanation:
Grahams law states that the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight. In the same conditions of temperature and pressure, the molar mass is proportional to the mass density. Therefore the rate of diffusion of different gases is inversely proportional to the square root of their mass densities.
r a ($$\sqrt{\frac {1}{d}}$$)
and r a ($$\sqrt{\frac {1}{M}}$$)

Question 3.
The rate of diffusion methane is twice that of X. The molecular mass of X is
(a) 64.0
(b) 32.0
(c) 40
(d) 80

Explanation:
Let rate of diffusion of gas x, r1 = a
Therefore, rate of diffusion of methane, r2 = 2 a
According to Grahams Law of Diffusion
($$\frac {r_1}{r_2}$$) = ($$\sqrt{\frac {M_2}{M_1}}$$)
M1 = Molecular mass of gas x
M2 = Molecular mass of Methane = 16 g
Therefore, ($$\frac {a}{2a}$$) = ($$\sqrt{\frac {16}{M_2}}$$)
Squaring both the sides, ($$\frac {1}{4}$$) = ($$\frac {16}{M_2}$$)
or, M2 = 16 × 4 = 64 g

Question 4.
The state of matter that shows the uniformity of behavior :
(a) Solid Liquid
(b) Liquid
(c) Gas
(d) None of the Above

Explanation:
Of the three states of matter, the gaseous state is the simplest and shows greatest uniformity in behaviour. Gases show almost similar behaviour irrespective of their chemical nature. This state is characterized by:
Gases maintain neither the volume nor the shape. They completely fill the container in which they are placed.

They expand appreciably on heating. Gases are highly compressible. The volume of the gas decreases when the pressure increases. They diffuse rapidly into space. Gases exert equal pressure in all directions.
All gases are colourless except a few e.g. chlorine (greenish yellow) bromine (reddish brown), nitrogen dioxide (reddish brown)

The behaviour of gases can be described by certain quantitative relationships called gas laws. They give the relationship between mass, pressure, volume and temperature.

Question 5.
A gas deviates from ideal behavior at a high pressure because its molecules:
(a) Attract one another
(b) Show the Tyndall Effect
(c) Have kinetic energy
(d) Are bound by covalent bonds

Explanation:
The basic concept of the kinetic-molecular theory give us the information why real gases deviate from ideal behavior. The molecules of an ideal gas are assumed to occupy no space and have no attractions for one another. Real molecules, however, do have finite volumes, and they do attract one another. So, a gas deviates from ideal behavior at a high pressure because its molecules attract one another.

Question 6.
The value of universal gas constant R depends on
(a) Temperature of Gas
(b) Volume of Gas
(c) Number of Moles of Gas
(d) Units of Volume,Temperature and Pressure

Answer: (d) Units of Volume,Temperature and Pressure
Explanation:
The value of the gas constant R depends on the units used for pressure, volume and temperature.

Question 7.
The critical volumes of four gases A, B, C, D are respectively 0.025 L, 0.312 L, 0.245 L, 0.432 L, the gas with highest value of van der Wall constant b is
(a) A
(b) B
(c) C
(d) D

Explanation:
Vc = 3b = 3 × 4N × (4/3) pr³

Question 8.
Which of the following statement is wrong for gases?
(a) Gases do not have definite shape and volume
(b) Volume of the gas is equal to the volume of the container confining the gas
(c) Confined gas exert uniform pressure on the wall of the container in all directions
(d) Mass of the gas cannot be determined by weighing a container in which it is contained

Answer: (d) Mass of the gas cannot be determined by weighing a container in which it is contained
Explanation:
Mass of the gas = mass of the cylinder including gas – mass of empty cylinder. So mass of a gas can be determined by weighing the container in which it is enclosed. Thus, the statement (d) is wrong for gases.

Question 9.
In van der Waal equation of state of gas laws, the constant b is a measure of
(a) Intermolecular collisions per unit volume
(b) Intermolecular attraction
(c) Volume occupied by the molecules
(d) Intermolecular repulsions

Answer: (c) Volume occupied by the molecules
Explanation:
In van der Waals equation of state of the gas law, the constant b is a measure of the volume occupied by the molecules. It gives the effective size of the gas molecules. The greater value of b indicates a larger size of the molecules and smaller compressible volume.

Question 10.
The volume of 2.8 g of carbon monoxide at 27°C and 0.0821 atm is
(a) 30 L
(b) 3 L
(c) 0.3 L
(d) 1.5 L

Explanation:
According to the ideal gas equation, we have
PV = nRT
?PV = ($$\frac {w}{M}$$) RT
?V = ? ($$\frac {w}{M}$$) ($$\frac {RT}{P}$$)
Given values are:
w = 2.8 g
M = Molar mass of CO = 28 g mol-1
T = 27°C = (273 + 27) = 300 K
P = 0.821 atm
R = 0.0821 L atm mol-1 K-1
Putting the values in the formula we get :
V = (2.8 g /28 g mol-1) × (0.0821 L atm mol-1 K-1) × (300 K)/(0.821 atm)
= 3 L

Question 11.
If 20cm³ gas at 1 atm. is expanded to 50 cm³ at constant T, then what is the final pressure
(a) 20 × 150
(b) 50 × 120
(c) 1 × 120 × 50
(d) None of these

Explanation:
At constant T, P1V1 = P2V2
1 × 20 = P2 × 50;
P2 = ($$\frac {20}{ 50}$$) × 1

Question 12.
The vapour pressure of water at 300 K in a closed container is 0.4 atm. If the volume of container is doubled, its vapour pressure at 300 K will be
(a) 0.8 atm
(b) 0.2 atm
(c) 0.4 atm
(d) 0.6 atm

Explanation:
Vapour pressure depends on T only and it does not depend on container volume.

Question 13.
Name the liquid with higher vapour pressure in the following pairs:
(a) Alcohol, glycerine (b) Petrol, kerosene (c) mercury, water.
(a) Alcohol, Water, Petrol
(b) Petrol, Water, Alcohol
(c) Alcohol, Petrol, Water
(d) None of these

Explanation:
The vapour pressure of the liquid is inversely proportional to the magnitude of the intermolecular forces of attraction present. Based on this, the liquid with higher vapour pressure in the different pairs is: (a) Alcohol, (b) Petrol, (c) Water.

Question 14.
The rise or fall of a liquid within a tube of small bore is called:
(a) Surface Tension
(b) Capillary Action
(c) Viscosity
(d) Formation of Curvature

Explanation:
Capillarity, rise or depression of a liquid in a small passage such as a tube of small cross-sectional area, like the spaces between the fibres of a towel or the openings in a porous material. Capillarity is not limited to the vertical direction. Water is drawn into the fibres of a towel, no matter how the towel is oriented.

Liquids that rise in small-bore tubes inserted into the liquid are said to wet the tube, whereas liquids that are depressed within thin tubes below the surface of the surrounding liquid do not wet the tube. Water is a liquid that wets glass capillary tubes; mercury is one that does not. When wetting does not occur, capillarity does not occur.

Capillarity is the result of surface, or interfacial, forces. The rise of water in a thin tube inserted in water is caused by forces of attraction between the molecules of water and the glass walls and among the molecules of water themselves. These attractive forces just balance the force of gravity of the column of water that has risen to a characteristic height. The narrower the bore of the capillary tube, the higher the water rises. Mercury, conversely, is depressed to a greater degree, the narrower the bore.

Question 15.
The theory which explains that gases consist of molecules, which are in rapid option is known as:
(a) Daltons Atomic Theory
(b) Bohrs Theory
(c) Rutherfords Atomic Theory
(d) Kinetic Molecular Theory

Explanation:
The kinetic molecular theory (KMT) is a simple microscopic model that effectively explains the gas laws described in previous modules of this chapter. This theory is based on the following five postulates described here. (Note: The term “molecule” will be used to refer to the individual chemical species that compose the gas, although some gases are composed of atomic species, for example, the noble gases.)

Gases are composed of molecules that are in continuous motion, travelling in straight lines and changing direction only when they collide with other molecules or with the walls of a container.
The molecules composing the gas are negligibly small compared to the distances between them.
The pressure exerted by a gas in a container results from collisions between the gas molecules and the container walls.

Gas molecules exert no attractive or repulsive forces on each other or the container walls; therefore, their collisions are elastic (do not involve a loss of energy).
The average kinetic energy of the gas molecules is proportional to the kelvin temperature of the gas.

Question 16.
If helium and methane are allowed to diffuse out of the container under the similar conditions of temperature and pressure, then the ratio of rate of diffusion of helium to methane is:
(a) 2 : 1
(b) 1 : 2
(c) 3 : 5
(d) 4 : 1

Explanation:
According to Grahams law
($$\frac {r_1}{r_2}$$) = ($$\sqrt{\frac {M_1}{M_2}}$$)
(rHe/rCH4) = ($$\sqrt{\frac {16}{4}}$$)
= ($$\frac {1}{2}$$)

Question 17.
When you heat a sample of gas, what happens to the particles that make up the gas?
(a) The particles move faster.
(b) The particles break apart
(c) The particles get smaller
(d) The particles become more dense

Answer: (a) The particles move faster.
Explanation:
There is a great deal of empty space between particles, which have a lot of kinetic energy. The particles move very fast and collide into one another when the gas is heated up, causing them to diffuse, or spread out, until they are evenly distributed throughout the volume of the container.

Question 18.
The law, which states that at constant temperature, the volume of a given mass of gas is inversely proportional is pressure, is known as:
(a) Boyles law
(b) Charles law
(c) Combine gas law

Explanation:
In 1662 Robert Boyle studied the relationship between volume and pressure of a gas of fixed amount at constant temperature. He observed that volume of a given mass of a gas is inversely proportional to its pressure at a constant temperature. Boyles law, published in 1662, states that, at constant temperature, the product of the pressure and volume of a given mass of an ideal gas in a closed system is always constant. It can be verified experimentally using a pressure gauge and a variable volume container. It can also be derived from the kinetic theory of gases: if a container, with a fixed number of molecules inside, is reduced in volume, more molecules will strike a given area of the sides of the container per unit time, causing a greater pressure.
A statement of Boyles law is as follows:
The volume of a given mass of a gas is inversely related to pressure when the temperature is constant.?
V ? ($$\frac {1}{P}$$) meaning “Volume is inversely proportional to Pressure”, or
P ? ($$\frac {1}{V}$$) meaning “Pressure is inversely proportional to Volume”, or
where P is the pressure, and V is the volume of a gas, and k1 is the constant in this equation.

Question 19.
How many of the know elements exist as gases at 25°C?
(a) 9
(b) 11
(c) 12
(d) 15

Question 20.
The states of matter having no definite shape but definite volume:
(a) Gas
(b) Liquid
(c) Solid
(d) None of the Above

Explanation:
In a liquid, particles will flow or glide over one another, but stay toward the bottom of the container. The attractive forces between particles are strong enough to hold a specific volume but not strong enough to keep the molecules sliding over each other.

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