states-of-matter-quiz-3

States of Matter Quiz-3

Dear Readers,

The one subject in NEET which is candidates who can easily attain good marks is Chemistry. That's the reason, often, one doesn’t pay notice and choose to compromise it. But if one wants to rank above others, the tip is to be thorough with NEET chemistry concepts. The understanding of reactions and definite basic understanding is what requires major attention in Chemistry but once done it only gets simpler from there. The main focus on the to-do list should be on getting a hang of the NCERT syllabus of NEET chemistry..

Q1. The rate of diffusion of methane at a given temperature is twice that of gas X. The molecular mass of gas X is

•  64.0
•  32.0
•  4.0
•  8.0

Solution
(a) Let the rate of diffusion of gas x=a and molecular mass =M So, r_x=a,M_x=M r_CH4=2a,M_CH4=16 r_x/r_CH4 =√(M_CH4/M_x ) or a/2a=√(16/M_x ) or M_x=64  

Q2.The molecular weight of O₂ and SO₂ are 32 and 64 respectively. If one litre of O₂ at 15℃ and 759 mm pressure contains N molecules, the number of molecules in two litre of SO₂ under the same conditions of temperature and pressure will be:

•  N/2
•  N
•  2N
•  4N

Solution

(c) V∝ mole at same P and T.

Q3. Surface tension of water is 73 dyne cm^-1 at 20℃. If surface area is increased by 0.10 m², work done is 

•  7.3 erg
•  7.3×10⁴ erg
•  73 J
•  0.73 J

Solution
(b) Work done = surface tension × increase in area =73×0.10=73×0.10×10⁴ =7.3×10⁴ erg

Q4. The rms speed of N₂ molecules in a gas is u. If the temperature is doubled and the nitrogen molecules dissociate into nitrogen atoms, the rms speed becomes

•  u/2
•  2u
•  4u
•  14u

Solution
(b) u₁/u₂ =√((n₁ T₁)/(n₂ T₂ ))=√((n×T)/(2n×2T))=√(1/4 )=1/2 ∴ u₂=2u₁

Q5.Equal masses of ethane and hydrogen are mixed in an empty container at 25℃. The fraction of the total pressure exerted by hydrogen is

•  1 : 2
•  1 : 1
•  1 : 16
•  15:16

Solution
  (d) Moles of H₂=w/2, and ethane =w/30 Total mo. of moles =w/2+w/30=16w/30 Partial pressure of H₂=p×(w/2)/(16w/30) =w/2×30/16w=30/32=15/16  

Q6. Which is a postulate of kinetic theory of gases?

•  Gases combine in simple ratio
•  There is an attraction between gaseous molecules
•  There is no influence of gravity on gas molecules
•  Atom is indivisible

Solution
(c) Follow assumptions of kinetic theory.  

Q7.For 1 mole of gas, the average kinetic energy is given as E. The u_rms of gas is:

•  [2E/M]^1/2
•  [3E/M]^1/2
•  [2E/3M]^1/2
•  [3E/2M]^1/2

Solution

(a) Average kinetic energy,E=3/2 RT u_rms=√(3RT/M)=√(2E/M)

Q8.The number of collisions depends on:

•  Mean free path
•  Pressure
•  Temperature
•  All of these

Solution
(d) Collision frequency =u_rms/λ;u_rms depends on T,λ depends on P and T.  

Q9.Which of the following statement is not true?

•  The pressure of a gas is due to collision of the gas molecules with the walls of the container.
•  The molecular velocity of any gas is proportional to the square root of the absolute temperature.
•  The rate of diffusion of a gas is directly proportional to the density of the gas at constant pressure.
•  Kinetic energy of an ideal gas is directly proportional to the absolute temperature.

Solution

(c) According to Graham’s law the rate of diffusion is inversely proportional to square root of molecular weight and density. r∝1/√d and r∝1/√M

Q10. The edge of unit cell of fcc Xe crystal is 620 pm. The radius of Xe atom is

•  189.37 pm
•  209.87 pm
•  219.25 pm
•  235.16 pm

Solution

(c) r=a/(2√2)=620/(2√2)=219.25 pm