# Kinetic Theory of Gases – Question Paper 04

 1 The r.m.s. speed of the molecules of an enclosed gas is x. what will be the r.m.s. speed, if the pressure of the gas is doubled but the temperature is kept constant? (a) x (b) (c) 2x (d) Answer: (a) 2 According to kinetic theory of gases, at absolute zero of temperature (CBSE-90) (a) Water freezes (b) Liquid helium freezes (c) Molecular motion stops (d) Liquid hydrogen freezes Answer: (c) 3 A room temperature the r.m.s. velocity of the molecules of a certain diatomic gas is found to be 1930 m/sec. the gas is (IIT 84) (a) H2 (b) F2 (c) O2 (d) Cl2 Answer: (a) 4 The r.m.s velocity of the molecules of an ideal gas is C at a temperature of 100K. at what temperature is r.m.s. velocity will be doubted? (a) 200 K (b) 400 K (c) 300 K (d) 50 K Answer: (b) 5 One mole of mono atomic gas (γ = 5/3) is mixed with one mole of diatomic gas (γ = 7/5) what will be the value of γ for the mixture? (I.I.T-88) (a) 1.5 (b) 2.5 (c) 1.0 (d) 2 Answer: (a) 6 In a gas, 5 molecules have speed 150 m/s, 170 m/s, 170 m/s, 180 m/s, 190 m/s. ratio of Vrms to Vmean is nearly (MHT-CET-2002) (a) 1 (b) 3 (c) 0.5 (d) 0.04 Answer: (a) 7 The mean free path of nitrogen molecules at 27°C is 3 × 10– 7 m/s. if the average speed of nitrogen molecules at the same temperature is 600 m/s then the collision frequency will be (a) 109/sec (b) 1.5 × 109/sec (c) 2 × 109/sec (d) 3 × 109/sec Answer: (c) 8 The mean translational K.E. per unit volume E and the pressure P of a perfect gas are related as (Roorkee-92) (a) (b) (c) (d) Answer: (b) 9 If two gases of molecular weights M1 and M2 are at same pressure and temperature, ratio of their r.m.s. speed will be (ALL INDIA PMT-99) (a) M2: M1 (b) M1: M2 (c) (d) Answer: (d) 10 K.E. per unit volume is given by (MHT-CET 2003) (a) (b) (c) (d) None of these Answer: (a) 11 The volume of a gas 20°C is 100cm3 at normal pressure. If its is heated to 100°, its volume becomes 125 cm3 at the same pressure, then volume coefficient of the gas is (At normal pressure) (MHT-CET-2000) (a) 0.0033/°C (b) 0.0030/°C (c) 0.0025/°C (d) 0.0021/°C Answer: (a) 12 The temperature of a gas is –68°C. to what temperature should it be heated, so that the r.m.s. velocity of the molecules be doubled? (a) 357°C (b) 457°C (c) 547°C (d) 820°C Answer: (c) 13 The kinetic energy of one gm-molecule of a gas at normal temperature and pressure is (R = 8.31 J/mol-K) (MHCET-99, AFMC PUNE-98) (a) 0.56 × 104 J (b) 1.3 × 102 J (c) 2.7 × 102 J (d) 3.4 × 103 J Answer: (d) 14 Energy supplied to convert unit mass of substance from solid to liquid state at its melting point is called (MHT-CET 2003) (a) Latent heat of fusion (b) Evaporation (c) Solidification (d) Latent heat of fission Answer: (a) 15 The average translational K.E. of the molecules in a sample of oxygen at 300K is 6 × 10–20 J. what is the average translational energy at 750 K? (a) 2 × 10–19 J (b) 1.5 × 10–19 J (c) 3 × 10–18 J (d) 3.5 × 10–21 J Answer: (b) 16 Translational kinetic energy of gas molecule, for one mole of the gas, is equal (AFMC PUNE-95) (a) (b) (c) (d) Answer: (a) 17 Mean kinetic energy of perfect gas is (MHT-CET-2000) (a) ∝ T (b) ∝ T2 (c) (d) Answer: (a) 18 The volume of 2.8 gm of carbon monoxide (CO) at 27°C and 0.821 atm pressure is (R = 0.0821 litre atm/mol K) (MHT-CET-1999) (a) 0.3 litre (b) 1.5 litre (c) 3 litre (d) 60 litre Answer: (c) 19 The frequency of a light wave in a material is 3 × 1014 Hz and the wavelength is 6000 . What is the refractive index of the material? (a) (b) (c) (d) Answer: (c) 20 The temperature of a gas is raised from 27°C to 927°C. the root mean square speed (NCERT-83, CBSE-94) (a) times the earlier value (b) Gets halved (c) Remains the same (d) Gets doubled Answer: (d) 21 If 3 kg of mass is converted into energy. Energy released by (MHT-CET-2003) (a) 9 × 108 J (b) 9 × 1016 J (c) 27 × 108 J (d) 27 × 1016 J Answer: (d) 22 Which of the following is the unit of specific heat? (MHT-CET-2004) (a) J kg/°C (b) J/kg°C (c) kg °C/J (d) J kg/°C2 Answer: (b) 23 If CP – CV = R and , then which relation is correct. (MHT-CET 2006) (a) (b) (c) (d) Answer: (a) 24 Three containers of the same volume contains three different gases. The masses of the molecules are m1, m2 and m3 and number of molecules in their respective container are N1, N2 and N3. the gas pressure in the container are P1, P2, and P3 respectively. All the gasses are now mixed and put in one of these containers. The pressure P of the mixture is (CBSE-92) (a) P < (P1 + P2 + P3) (b) (c) P = (P1 + P2 + P3) (d) P > (P1 + P2 + P3) Answer: (c) 25 If 70 calories heat is required to raise the temperature of 2 moles of an ideal gas at constant pressure from 30°C to 35°C. the amount of heat required to raise the temperature of the same gas through the same range at constant volume is (I.I.T-85) (a) 20 cal (b) 30 cal (c) 40 cal (d) 50 cal Answer: (c)