states-of-matter-quiz-7

States of Matter Quiz-7

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. Frenkel defect is found in crystals in which the radius ration is

•  1.5
•  1.7
•  Very low
•  Slightly less than unity

Solution
(c) Frenkel defect is observed in the crystals in which the radius ratio is low  

Q2.Avogadro’s number is the number of molecules present at NTP in:

•  1 mL of gas
•  1 litre of gas
•  22.4 litre of gas
•  22.4 mL of gas

Solution

(c) Follow Avogadro’s hypothesis.

Q3. In which one of the following does the given amount of chlorine exert the least pressure in a vessel of capacity 1 dm³ at 273 K? 

•  0.0355g
•  0.071
•  6.023×10²¹ molecules
•  0.02 moles

Solution
(a) Ideal gas equation is Vp=nRT When V and T are same, p∝n Thus, when number of moles, i.e.,n is least, it will exert least pressure. (a) n=(wt.)/(mol.wt.)=0.0355/33.5=1×10^-3 mol (b) n=0.071/33.5=2×10^-3 mol (c) n=(number of molecules )/N_A =(6.023×10²¹)/(6.023×10²³ )=0.01 mol (d) n=0.02 mol Thus, 0.0335 g chlorine will exert the least pressure.

Q4. Which of the following statements is not true?

•  The ratio of the mean speed to the RMS speed is independent of the temperature
•  The square of the mean speed of the molecules is equal to the mean squared speed at a certain temperature
•  Mean kinetic energy of the gas molecules at any given temperature is independent of the mean speed
•  The difference between RMS speed and mean speed at any temperature for different gases diminishes as larger and yet larger molar masses are considered

Solution

Q5.

•  p₁>p₂
•  p₁<p₂
•  p₁=p₂
•  All of these

Solution
  (b) At constant pressure V∝T, but according to Gay Lussac’s law the pressure of a given mass of a gas is directly proportional to the absolute temperature. Thus, p₁<p₂  

Q6. Oxygen gas is collected by downward displacement of water in a jar. The level of water inside the jar is adjusted to the height of water outside the jar. When the adjustment is made, the pressure exerted by the oxygen is:

•  Equal to the atmospheric pressure
•  Equal to the vapour pressure of oxygen at that temperature
•  Equal to atmospheric pressure plus aqueous tension at that temperature
•  Equal to atmospheric pressure minus aqueous tension at that temperature

Solution
(d) P_{dry O2+Pwater vapour=Pwet O2}  

Q7.If the pressure of N₂/H₂ mixture in a closed vessel is 100 atmosphere and 20% of the mixture then reacts, the pressure at the same temperature would be:

•  The same
•  110 atmospheres
•  90 atmospheres
•  80 atmospheres

Solution

(c) 20% mixture produce 10% NH_3 N₂+3H₂→2NH₃ Thus, percentage remains 90%

Q8.A certain gas takes three times as long to effuse out as helium. Its molecular mass will be:

•  27 u
•  36 u
•  64 u
•  9 u

Solution


 

Q9.Volume occupied by molecules of one mole gas at NTP, each having radius of 10^-8 cm is:

•  22.0 litre
•  22.4 litre
•  10.9 mL
•  10.09 litre

Solution

(c) Volume of molecules in one mole =4×N×V=4×N×4/3 πr³ =4×6.023×10²³×4/3×22/7×(10^-8)³ =10.09 mL

Q10. At relatively high pressure, van der Waals’ equation reduces to:

•  PV=RT
•  PV=RT+a/V
•  PV=RT+Pb
•  PV=RT-a/V²

Solution

(c) At high pressure, volume of molecules should not be neglected in comparison to volume of gas. Also experimental studies reveals PV>RT at high P.