Chemistry

States of Matter

Question:

Use the information and data given below to answer the questions (a) to (c):
• Stronger intermolecular forces result in higher boiling point.
• Strength of London forces increases with the number of electrons in the molecule.
• Boiling point of HF, HC1, HBr and HI are 293 K, 189 K, 206 K and 238 K respectively.
(a) Which type of intermolecular forces are present in the molecules HF, HC1, HBr and HI?
(b) Looking at the trend of boiling points of HC1, HBr and HI, explain out of dipole-dipole interaction and London interaction, which one is predominant here?
(c) Why is boiling point of hydrogen fluoride highest while that of hydrogen chloride lowest?

Answer:

(a) All the given molecules viz. HF, HC1, HBr and HI have permanent di-poles. Hence, all of them possess dipole-dipole and London forces. HF in addition to dipole-dipole and London forces also has hydrogen bonding.
(b) Electronegativity of Cl, Br and I is in the order: Cl > Br > I. Therefore, polar character and hence dipole-dipole interactions should be in the order HCl > HBr > HI. But boiling points are found to be in the order HCl < HBr < HI. This shows that London forces are predominant. This is because London forces increase as the number of electrons in the molecule increases. In this case, the number of electrons increases from HC1 to HI.
(c) Due to very high electronegativity of F, HF is most polar and also there is hydrogen bonding present in it. Hence, it has the highest boiling point.

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States of Matter

Q 1.

Define an ideal gas.

Q 2.

The magnitude of surface tension of liquid depends on the attractive forces between the molecules. Arrange the following in increasing order of surface tension:

water, alcohol (C2H5OH) and hexane [CH3(CH2)4CH3)].

 

Q 3.

Explain the physical significance of vander Waals parameters.

Q 4.

Define boiling point of a liquid.

Q 5.

The critical temperature (Tc) and critical pressure (Pc) of C02 are 30.98 °C and 73 atm respectively. Can C02(g) be liquefied at 32 °C and 80 atm pressure?

Q 6.

Define critical temperature of gas.

Q 7.

With regard to the gaseous state of matter which of the following statements are correct?
(a) Complete order of molecules (b) Complete disorder of molecules
(c) Random motion of molecules (d) Fixed position of molecules

Q 8.

Explain the effect of increasing the temperature of a liquid on intermolecular forces operating between its particles. What will happen to the viscosity of a liquid if its temperature is increased?

Q 9.

Assertion (A): Liquids tend to have maximum number of molecules at their surface.
Reason (R): Small liquid drops have spherical shape.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Q 10.

What will be the minimum pressure required to compress 500 dm3 of air at 1 bar to 200 dm3 at 30 °C?

Q 11.

Name two phenomena that can be explained on the basis of surface tension.

Q 12.

Calculate the temperature of 4.0 moles of a gas occupying 5 dm3 at 3.32 bar (R = 0.083 bar  dm3 K-1 mol-1)

Q 13.

What is SI unit of (i) Viscosity (ii) Surface tension?

Q 14.

The behaviour of matter in different states is governed by various physical laws. According to you what are the factors that determine the state of matter?

Q 15.

Calculate the total number of electrons present in 1.4 g of dinitrogen gas.

Q 16.

What are real gases ?

Q 17.

Name four properties of gases.

Q 18.

What do you mean by aqueous tension?

Q 19.

What is the effect of temperatures on the vapour pressure of a liquid?

Q 20.

Give an expression for the van der Wools equation. Give the significance of the constants used in the equation. What are their units?

Q 21.

For real gases the relation between P, V and T is given by van der Waals equation:
ncert-exemplar-problems-class-11-chemistry-chapter-5-states-of-matter-8

where ‘a' and ‘b' are van der Waals constants, ‘nb' is approximately equal to the total volume of the molecules of a gas.
‘a' is the measure of magnitude of intermolecular attraction.
(i) Arrange the following gases in the increasing order of ‘b'. Give reason. 02, C02, H2, He
(ii) Arrange the following gases in the decreasing order of magnitude of ‘a'. Give reason.CH4, O2, H2

Q 22.

Assertion (A): Gases do not liquefy above their critical temperature, even on applying high pressure.
Reason (R): Above critical temperature, the molecular speed is high and intermolecular attractions cannot hold the molecules together because they escape because of high speed.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Q 23.

A vessel of 120 mL capacity contains a certain amount of gas at 35 °C and 1.2 bar pressure. The gas is transferred to another vessel of volume 180 mL at 35 °C. What would be its pressure?

Q 24.

Why does sharpened edge becomes smooth on heating up to melting point?

Q 25.

One of the assumptions of kinetic theory of gases is that there is no force of attraction between the molecules of a gas.
State and explain the evidence that shows that the assumption is not applicable for real gases.

Q 26.

Assertion (A): Three states of matter are the result of balance between intermolecular forces and thermal energy of the molecules. .
Reason (R): Intermolecular forces tend to keep the molecules together but thermal energy of molecules tends to keep them apart.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Q 27.

Density of a gas is found to be 5.46 g/dm3 at 27 °C and at 2 bar pressure. What will be its density at STP?

Q 28.

What do you understand by laminar flow of a liquid?

Q 29.

What is meant by elastic collision ?

Q 30.

Write van der Waals equation for n moles of a gas.

Q 31.

At 25 °C and 760 mm ofHg pressure a gas occupies 600 mL volume. What will be its pressure at a height where temperature is 10 °C and volume of the gas is 640 mL?

Q 32.

State and explain Dalton’s law of partial pressures. Can we apply Dalton's law of partial pressures to a mixture of carbon monoxide and oxygen?

Q 33.

Under which of the following two conditions applied together, a gas deviates most from the ideal behaviour?
(a) Low pressure (b) High pressure
(c) Low temperature (d) High temperature

Q 34.

Value of universal gas constant (R) is same for all gases. What is its physical significance?

Q 35.

One of the assumptions of kinetic theory of gases states that "there is no force of attraction between the molecules of a gas."How far is this statement correct? Is it possible to liquefy an ideal gas? Explain.

Q 36.

Pressure exerted by saturated water vapour is called aqueous tension. What correction term will you apply to the total pressure to obtain pressure of dry gas?

Q 37.

Viscosity of a liquid arises due to strong intermolecular forces existing between the molecules. Stronger the intermolecular forces, greater is the viscosity. Name the intermolecular forces existing in the following liquids and arrange them in the increasing order of their viscosities. Also give reason for the assigned order in one line.Water, Hexane (CH3CH2CH2CH2CH2CH3), Glycerine (CH2OHCH(OH)CH2OH)

Q 38.

Assertion (A): At constant temperature, PV vs V  plot for real gases is not a straight line.
Reason (R): At high pressure all gases have Z> 1 but at intermediate pressure most gases have Z < 1.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Q 39.

Isotherms of carbon dioxide at various temperatures are represented in the following figure. Answer the following questions based on this figure.
ncert-exemplar-problems-class-11-chemistry-chapter-5-states-of-matter-19

(i) In which state will C02 exist between the points a and b at temperature T1
(ii) At what point will Co2 start liquefying when temperature is T1?
(iii) At what point will C02 be completely liquefied when temperature is T2?
(iv) Will condensation take place when the temperature is T3
(v) What portion of the isotherm at T1 represent liquid and gaseous C02 at equilibrium?

Q 40.

What would be the SI unit for the quantity  PV2T2/n?

Q 41.

In terms of Charles’ law explain why -273 °C is the lowest possible temperature.

Q 42.

State Dalton's law of partial pressure.

Q 43.

Give mathematical expression for ideal gas equation.

Q 44.

(a) Why aerated water bottles kept under water during summer?
(b) Which property of liquid is responsible for spherical shape of drop?
(c) Why is moist air lighter than dry air?
(d) Define aqueous tension.
(e) What are units of a and b which are van der Waals constants?

Q 45.

Arrange the following in order of increasing density:
ncert-solutions-for-class-11th-chemistry-chapter-5-states-of-matter-33

Q 46.

Which of the following figures does not represent 1 mole of dioxygen gas at STP?
(a) 16 grams of gas                                                                
(b) 22.7 litres of gas
(c) 6.022 x 1023 dioxygen molecules
(d) 11.2 litres of gas

Q 47.

Physical properties of ice, water and steam are very different. What is the chemical composition of water in all the three states?

Q 48.

What will be the molar volume of nitrogen and argon at 273.15 K and 1 atm?

Q 49.

Two different gases ˜A' and ˜9' are filled in separate containers of equal capacity under the same conditions of temperature and pressure. On increasing the pressure slightly, the gas ˜A' liquefies but gas ˜B' does not liquefy even on applying high pressure until it is cooled. Explain this phenomenon.

Q 50.

Name the energy which arises due to motion of atoms or molecules in a body. How is this energy affected when the temperature is increased?