All Free Physics MCQs with Answers
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13,934 questions · page 696 of 697
- A. Molecules do not exert any force on each other
- B. The size of molecules is much larger than the separation between the molecules
- C. A finite volume of gas consists of a very small number of molecules
- D. The gas molecules are not in random motion
Explanation: A postulate of the kinetic theory of gases is that molecules exert no force on one another except during the instant of collision, which…
Correct answer: Molecules do not exert any force on each other- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: Root mean square speed follows from PV = (1/3)Nm<v^2>, giving v_rms = sqrt(3PV/Nm), equivalently sqrt(3kT/m) for one molecule or…
Correct answer: Option A- A. Collisions between gas molecules occur
- B. Collisions between gas molecules occur linearly
- C. Collisions must be elastic
- D. Collisions must be inelastic
Explanation: The kinetic theory assumes collisions between gas molecules are perfectly elastic, so kinetic energy is conserved in every collision.
Correct answer: Collisions must be elastic- A. 4 root mean square of oxygen
- B. ¼ root mean square of oxygen
- C. 1/16 root mean square of oxygen
- D. 1/6 root mean square of oxygen
Explanation: At the same temperature v_rms is inversely proportional to the square root of molecular mass, since v_rms = sqrt(3kT/m).
Correct answer: 4 root mean square of oxygen- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: Mean square speed is the average of the squares of the molecular speeds, <v^2> = (v1^2 + v2^2 + ...
Correct answer: Option B- A. N/a^2
- B. m/a^3
- C. Nm/a^3
- D. Na^3/m
Explanation: Density is total mass divided by total volume. N molecules of mass m each give a total mass of Nm, and a cube of side a has volume a^3, so…
Correct answer: Nm/a^3- A. n = NNA
- B. n = N/NA
- C. n = NA/N
- D. n = N + NA
Explanation: The number of moles is the number of molecules divided by Avogadro's number: n = N/NA.
Correct answer: n = N/NA- A. 496.38 K
- B. 438.96 K
- C. 0
- D. 496.38 oF
Explanation: A constant-volume gas thermometer gives T = T_triple x (P/P_triple), with the triple point of water at 273.16 K.
Correct answer: 496.38 K- A. Avogadro's constant
- B. Charles constant
- C. Newton's constant
- D. Boltzmann's constant
Explanation: The universal gas constant divided by Avogadro's number is the Boltzmann constant, k = R/NA = 1.38 x 10^-23 J/K.
Correct answer: Boltzmann's constant- A. Charles Law
- B. Avogadro's Law
- C. Newton's Constant
- D. Ideal Gas Law
Explanation: PV = nRT is the ideal gas law, which combines Boyle's law, Charles's law and Avogadro's law into a single equation of state.
Correct answer: Ideal Gas Law- A. 1 x 10³ Pa
- B. 2.5 x 10² Pa
- C. 1 x 10² Pa
- D. 2.7 x 10³ Pa
Explanation: Kinetic theory gives P = (1/3) x density x mean square speed. Substituting, P = (1/3) x 6 x 500 = 1000 Pa, which is 1 x 10^3 Pa.
Correct answer: 1 x 10³ Pa- A. 227K
- B. 300K
- C. 370K
- D. 390K
Explanation: Rearranging the ideal gas law gives T = PV/nR = (2.50 x 10^5 x 1.00 x 10^-2)/(1 x 8.314) = 2500/8.314 = 300 K.
Correct answer: 300K- A. 361K
- B. 298K
- C. 273K
- D. 250K
Explanation: For a fixed mass of gas the thermometer relation is T = T_triple x (PV)/(Pf Vf), with the triple point of water at 273.16 K.
Correct answer: 361K- A. 20X
- B. 300X
- C. 200X
- D. 2X
Explanation: Average kinetic energy is proportional to absolute temperature, not to Celsius temperature, so convert first: 27 C is 300 K and 327 C is…
Correct answer: 2X13915. The wavelength,of last spectral line in Lyman series in terms of Rydberg constant(R) is equal to:
- A. R
- B. R2
- C. 1/R
- D. 1/R2
Explanation: The last line of a series is its series limit, where the electron falls from n = infinity.
Correct answer: 1/R- A. Balmer series
- B. Lyman series
- C. Paschen series
- D. Pfund series
Explanation: Transitions that end on the third orbit produce the Paschen series, which lies in the infrared.
Correct answer: Paschen series- A. ⅓ mean K.E/volume
- B. ½ Mean K.E/volume
- C. ⅔ mean K.E/volume
- D. Mean K.E/volume
Explanation: Starting from PV = (1/3)Nm<v^2> and writing the mean kinetic energy per molecule as (1/2)m<v^2>, the pressure becomes P = (2/3) x (total…
Correct answer: ⅔ mean K.E/volume- A. Qualitative
- B. Quantitative
- C. Both A and B
- D. None of these
Explanation: The statement carries both kinds of information at once. It is qualitative in saying mercury is denser than water, and quantitative in…
Correct answer: Both A and B- A. double
- B. one fourth
- C. four times
- D. half
Explanation: Density is mass divided by volume and the mass of gas is fixed, so doubling the volume at constant temperature halves the density.
Correct answer: half- A. decreases
- B. remains constant
- C. is zero
- D. increase
Explanation: The second law of thermodynamics says the entropy of an isolated system increases in every irreversible process.
Correct answer: increase