States of Matter

Pressure versus volume graph for a real gas and an ideal gas is shown in Fig. 5.4. Answer the following questions based on this graph. (i) Interpret the behaviour of real gas with respect to an ideal gas at low pressure. (ii) Interpret the behaviour of real gas with respect to an ideal gas at high pressure. (iii)Mark the pressure and volume by drawing a line at the point where real gas behaves as an ideal gas.

(i) At low pressure as the dark blue curve and the sky blue curve are approaching each other, it shows that the real gas is behaving as an ideal gas at a low pressure. (ii) At high pressure as the...

The variation of pressure with the volume of the gas at different temperatures can be graphically represented as shown in Fig. 5.3. Based on this graph answer the following questions. (i) How will the volume of a gas change if its pressure is increased at constant temperature? (ii) At constant pressure, how will the volume of a gas change if the temperature is increased from 200K to 400K?

(i) As the temperature is constant, and the pressure is increasing and the change in the volume is seen as exponentially decreasing. (ii) At constant pressure, by increasing the temperature there is...

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?

As the temperature increases, the intermolecular force operating between the particles decreases, the bond strength increases and also the kinetic energy increases. Hence, as the temperature...

The relation between the pressure exerted by an ideal gas (Pideal) and observed pressure (Pearl) is given by the equation: Pideal = Preal+ an2/V2 If the pressure is taken in Nm-2, the number of moles in mol and volume in m3, Calculate the unit of ‘a’. What will be the unit of ‘a’ when pressure is in atmosphere and volume in dm3?

We know that: Pideal = Preal + an2/V2 Pideal – Preal= an2/V2 Nm-2 = a*mol2/m6 A = Nm4mol-2 The unit of ‘a’ when the pressure is taken in Nm-2, number of moles in “mol” and volume in m3 is Nm4mol-2...

For real gases the relation between p, V and T are given by van der Waals equation: [(P + an2) / V2](V – nb) = nRT 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 the magnitude of intermolecular attraction. (i) Arrange the following gases in the increasing order of ‘b’. Give reason. O2, CO2, H2, He (ii) Arrange the following gases in the decreasing order of magnitude of ‘a’. Give reason. CH4, O2, H2

(i) The increasing order of ‘b’ is as follows: He < H2< O2< CO2. As the Vander Waals constant ‘b’ is approximately equal to the total volume of the molecules of a gas. (ii)The decreasing...

The critical temperature (Tc) and critical pressure (Pc) of CO2 are 30.98°C and 73atm respectively. Can CO2(g) be liquefied at 32°C and 80atm pressure?

CO2 gas cannot be liquefied at a temperature which is greater than its critical temperature i.e 30.98°C even by applying any pressure. So as the given temperature is 32°C by applying a pressure of...

Compressibility factor, Z, of a gas is given as Z = PV/ nRT (i) What is the value of Z for an ideal gas? (ii) For real gas what will be the effect on the value of Z above Boyle’s temperature?

(i) Compressibility factor, Z is defined as the ratio of the product of pressure and volume to the product of the number of moles, gas constant and temperature. For an ideal gas, the value of Z is...

One of the assumptions of the 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.

Under a condition of low pressure and high temperature the assumption made by kinetic theory is true. At high temperature, the molecules will be very far from each other and at low pressure, the...

Name two intermolecular forces that exist between HF molecules in a liquid state.

Hydrogen bonding and dipole-dipole interaction (HF-HF interaction) exists between HF molecule in a liquid state.

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

Thermal energy arises due to the motion of particles (atoms or molecules) in the body. If we increase the temperature then the kinetic energy of atom and molecule increases significantly and they...

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

The total pressure of the gas is Pmoist gas = Pdry gas By applying the correction term, we have: Pdry gas = Pmoist gas – Aqueous tension Therefore, the correction term applied to the total pressure...

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

H2O exists in three different states of matter. It exists in the solid form as ice, in the liquid form as water and as steam in the gaseous state. All of these states consist of water, due to which...

Which of the following figures does not represent 1 mole of dioxygen gas at STP? (i) 16 grams of gas (ii) 22.7 litres of gas (iii) 6.022 × 1023 dioxygen molecules (iv) 11.2 litres of gas

The correct options are (i) and (iv).

With regard to the gaseous state of matter which of the following statements are correct? (i) Complete order of molecules (ii) Complete disorder of molecules (iii) Random motion of molecules (iv) Fixed position of molecules

Option (ii) and (iii) are the correct statements.

How does the surface tension of a liquid vary with an increase in temperature? (i) Remains the same (ii) Decreases (iii) Increases (iv) No regular pattern is followed

The correct option is (ii) Decreases.

Which curve in Fig. 5.2 represents the curve of an ideal gas? (i) B only (ii) C and D only (iii) E and F only (iv) A and B only

The correct option is (i) B only.

Atmospheric pressures recorded in different cities are as follows: Cities Shimla Bangalore Delhi Mumbai p in N/m2 1.01×105 1.2×105 1.02×105 1.21×105. Consider the above data and mark the place at which liquid will boil first. (i) Shimla (ii) Bangalore (iii) Delhi (iv) Mumbai

The correct option is (i) Shimla

Gases possess characteristic critical temperature which depends upon the magnitude of intermolecular forces between the particles. Following are the critical temperatures of some gases. Gases H2 He O2 N2 Critical temperature in Kelvin 33.2 5.3 154.3 126 From the above data what would be the order of liquefaction of these gases? Start writing the order from the gas liquefying first (i) H2, He, O2, N2 (ii) He, O2, H2, N2 (iii) N2, O2, He, H2 (iv) O2, N2, H2, He

The correct option is (iv) O2, N2, H2, He.

As the temperature increases, the average kinetic energy of molecules increases. What would be the effect of the increase of temperature on pressure provided the volume is constant? (i) increases (ii) decreases (iii) remains the same (iv) becomes half

The correct option is (i) increases.

The pressure of a 1:4 mixture of dihydrogen and dioxygen enclosed in a vessel is one atmosphere. What would be the partial pressure of dioxygen? (i) 0.8×105 atm (ii) 0.008 Nm–2 (iii) 8×104 Nm–2 (iv) 0.25 atm

The correct option is (iii) 8×104 Nm–2

Dipole-dipole forces act between the molecules possessing permanent dipole. Ends of dipoles possess ‘partial charges’. The partial charge is (i) more than unit electronic charge (ii) equal to unit electronic charge (iii) less than unit electronic charge (iv) double the unit electronic charge

The correct option is (iii) less than unit electronic charge.

A plot of volume (V) versus temperature (T) for a gas at constant pressure is a straight line passing through the origin. The plots at different values of pressure are shown in Fig. 5.1. Which of the following order of pressure is correct for this gas? (i) p1 > p2 > p3 > p4 (ii) p1 = p2 = p3 = p4 (iii) p1 < p2 < p3 < p4 (iv) p1 < p2 = p3 < p4

The correct option is (iii) p1 < p2 < p3 < p4.

A person living in Shimla observed that cooking food without using pressure cooker takes more time. The reason for this observation is that at high altitude: (i) pressure increases (ii) temperature decreases (iii) pressure decreases (iv) temperature increases

The correct option is (iii) pressure decreases.

What is the experimental evidence in support of the idea that electronic energies in an atom are quantized?

The bright line spectrum shows that the atomic energy levels are measured. These lines are found to be the result of electronic transitions between energy and the atomic spectrum would have shown...