# Kinetic Theory of Gases – Question Paper 02

 1 Mass of gas is 300 gm and its specific heat at constant volume is 750J/kg K. if gas is heated through 75°C at constant pressure of 105 N/m2, it expands by volume 0.08 × 106 cm3. find CP/CV. (MHT-CET-2004) (a) 1.4 (b) 1.374 (c) 1.474 (d) 1.5 Answer: (d) 2 At what temperature, the rms speed of gas molecules I half the value at NTP? (MHT-CET-2004) (a) 68.25 K (b) 273 K (c) 345 K (d) 0 K Answer: (a) 3 The r.m.s. speed of the molecules of a gas in a vessel is 200 m/s. if 25% of the gas leaks out of the vessel, at constant temperature, then the r.m.s. speed of the remaining molecules will be (a) 400 m/s (b) 150 m/s (c) 100 m/s (d) 200 m/s Answer: (d) 4 For hydrogen gas CP – CV = a, and for oxygen gas CP – CV = b, so that relation between a and b given by (C.B.S.E-93) (a) a = 16 b (b) 16 a = b (c) a = b (d) a = 4 b Answer: (c) 5 A gas expands adiabatically at constant pressure such that its temperature T ∝ 1/ . The value of CP/CV of the gas is (MHT-CET-2004) (a) 1.30 (b) 1.50 (c) 1.67 (d) 2.00 Answer: (b) 6 A wall is hit elastically and normally by n balls per second, all the balls have the same mass m and are moving with the same velocity u. the force exerted by the balls on the wall is (a) mnu2 (b) 2 mnu2 (c) 2 mnu (d) Answer: (c) 7 The temperature at which the r.m.s. velocity of H2 becomes escape velocity from the earth is, (RAJ.P.E.T-97) (a) 10059 °C (b) 10059 K (c) 10332 °C (d) 10332 K Answer: (b) 8 The root mean square speed of hydrogen molecules at 300 K is 1930 m/s. then the root mean square speed of oxygen molecules at 900 K will be (MHT-CET-2002) (a) 1930 m/s (b) 836 m/s (c) 643 m/s (d) m/s Answer: (b) 9 A molecule of mass m moving with a velocity v makes 5 elastic collisions with a wall of the container per second. The change in its momentum per second will be (a) mv (b) 5 mv (c) (d) 10 mv Answer: (d) 10 Speed of 3 molecules of a gas are 3 m/s, 4 m/s and 5 m/s. R.m.s. speed of these molecule is, (C.P.M.T-93) (a) 4.8 m/s (b) 4.08 m/s (c) 4.5 m/s (d) 4 m/s Answer: (b) 11 What is the true for 3 moles of a gas? (MHT-CET-2002) (a) 3 (CP – CV) = R (b) (c) CP – CV = R (d) CP – 3CV = R Answer: (c) 12 K.E. per unit volume is given by (MHT-CET-2003) (a) (b) (c) (d) None of these Answer: (a) 13 The pressure exerted in terms of total kinetic energy per unit volume (E) is (MHT-CET-2005) (a) 3/2 E (b) E (c) 2/3 E (d) E Answer: (c) 14 At what temperature, the r.m.s. speed of the molecules of a gas is half its value at NTP? (a) 0 K (b) 273 K (c) 150 K (d) 68.25 K Answer: (d) 15 The difference between the principal specific heats of nitrogen is 300 J/kg-K and ratio of the two specific heats is 1.4 then (MHT CET 99) (a) CP = 1050 J/kg-K (b) CP = 750 J/kg-K (c) CP = 650 J/kg-K (d) CP = 150 J/kg-K Answer: (a) 16 Calculate the RMS velocity of molecules of a gas of which the ratio of two specific heats is 1.42 and velocity of sound in the gas is 500 m/s (MHT-CET-2001) (a) 727 m/s (b) 527 m/s (c) 927 m/s (d) 750 m/s Answer: (a) 17 PV/3 = RT, V represents volume of (MHT-CET-2002) (a) Any amount of gas (b) 2 moles of gas (c) 3 moles of gas (d) 4 moles of gas Answer: (c) 18 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) 19 If 2 kcal, of heat is supplied to a system cause to change the internal energy of a gas is 5030J, and external work done is 3350 J, then what is mechanical equivalent of heat? (MHT-CET-2003) (a) 41.90 J/kcal (b) 4190 J/cal (c) 4.19 J/kcal (d) 4.19 J/cal Answer: (d) 20 The average kinetic energy of the molecules of a gas at 27°C is 9 × 10–20 J. what is its average K.E. at 227°C? (a) 5 × 10–20 J (b) 10 × 10–20 J (c) 15 × 10–20 J (d) 20 × 10–20 J Answer: (c) 21 For a gas, the r.m.s. speed at 800K is (MP-PMT-97) (a) Half the value at 200 K (b) Double the value at 200 K (c) Same as at 200 K (d) Four times the value at 200 K Answer: (b) 22 The internal energy of one mole of an ideal gas depend upon (CPMT 74) (a) Volume of gas (b) Temperature of gas (c) Nature of gas (d) Density of gas Answer: (b) 23 The root mean square speed of hydrogen molecules at 300K is 1930 m/s. then the root mean square speed of oxygen molecule at 900K will be (MHT-CET-2001) (a) 1930 m/s (b) 838 m/s (c) 643 m/s (d) Answer: (b) 24 Which of the statement is true (MHT-CET 2005) (a) R = (γ – 1) CV (b) R = (γ + 1) CV (c) CV = R(γ + 1) (d) Answer: (a) 25 If at same temperature and pressure, the densities for two diatomic gases are respectively d1 and d2, then the ratio of velocities of sound in these will be (MHT-CET-2000) (a) (b) (c) d1d2 (d) Answer: (a)