chem mcq!

[zain tariq]

Q.58 Kp and Kc for a gaseous reversible chemical reaction may be same or different. Select
the reaction for which the two constants have same numerical value:
A) N2 + 3H2 into 2NH3
B) PCl5 into PCl3 + Cl2
C) N2 + O2 into 2NO
D) 2SO3 into 2SO2 +O2

Saw it in an Mcat paper...does'nt make sense!

 

[kshumaila52]

Q.58 Kp and Kc for a gaseous reversible chemical reaction may be same or different. Select
the reaction for which the two constants have same numerical value:
A) N2 + 3H2 into 2NH3
B) PCl5 into PCl3 + Cl2
C) N2 + O2 into 2NO
D) 2SO3 into 2SO2 +O2

Saw it in an Mcat paper...does'nt make sense!

Ans c
When no of moles of reactant are equal to number of moles of product then Kc=Kp

 

[destined007]

yes its c
If Kp=Kc
In this case there is no change in volume

If Kp>Kc
In this case reaction occur with the increase in volume.

If Kp<Kc
In this case reaction occur with the decrease in volume.

in A, volume decreases (Total number of moles of reactant is greater than the total number of moles of product)
in B, volume increases (Total number of moles of reactant is less than the total number of moles of product)
in C, volume remain same (Total number of moles of reactant is same as the total number of moles of product)
in D, volume increases (Total number of moles of reactant is less than the total number of moles in product)

 

[zain tariq]

well we never studied this in A levels!

 

[destined007]

yup. That is why when you are preparing for MCAT, take test tuition.

 

[zain tariq]

Q.12 Total energy of a body executing simple harmonic motion is directly proportional to:
A) The amplitude
B) Square root of amplitude
C) Reciprocal of amplitude
D) Square of amplitude

 

[zain tariq]

Q.4 A man in an elevator ascending with an acceleration will conclude that his weight
has:
A) Decreased
B) Increased
C) Reduced to zero
D) Remained constant

 

[aquariangurl]

Q.4 A man in an elevator ascending with an acceleration will conclude that his weight
has:
A) Decreased
B) Increased
C) Reduced to zero
D) Remained constant

It's A)Decreased. Because weight = mass x gravity. As we rise, gravity decreases, so weight decreases, but mass remains constant.

 

[zain tariq]

but i donot think that decrease in gravity will have a noticable effect...there must be some other reason..

 

[zain tariq]

Which property is not shown by real and ideal gases?
A) They fill all the space available to them.
B) They expand when heated.
C) They exert pressure on the walls of the
container.
D) The pressure decreases as the temperature is increased

 

[zain tariq]

in option D of the previous question i have a confusion ;is there a law dealing with pressure and temprature...like boyles law relates pressure and volume and charles law relates volume and temprature but how can we predict the effect of temprature on pressure....it looks as if the pressure will increase but volume will also increase!

 

[destined007]

Q.4 A man in an elevator ascending with an acceleration will conclude that his weight
has:
A) Decreased
B) Increased
C) Reduced to zero
D) Remained constant

The answers is B
When elevator is at rest or moving with constant velocity, the force used to lift the body = weight of the body
when the elevator is accelerating upwards with acceleration a, the force used to lift is F=mg + ma
When the elevator is acceleration downward with acceleration a, the force is F=mg - ma
The gravity itself doesn't change but the force acting changes.

 

[destined007]

Q.12 Total energy of a body executing simple harmonic motion is directly proportional to:
A) The amplitude
B) Square root of amplitude
C) Reciprocal of amplitude
D) Square of amplitude

its D
T.E=1/2mω^2x^2

 

[destined007]

Which property is not shown by real and ideal gases?
A) They fill all the space available to them.
B) They expand when heated.
C) They exert pressure on the walls of the
container.
D) The pressure decreases as the temperature is increased

Its D
in term of movement of particles: (for constant volume, ie, closed container)
When temperature is increased, the molecules gain kinetic energy and their motion increases. Their frequency of effective collision with one another and the walls of the container increases. Therefore, pressure increases.
(However, pressure may decrease with the increase in temperature but that only happens in the atmosphere)

in term of ideal gas law:
PV=nRT
P is proportional to temperature and inversely proportional to volume.

 

[aashernaqvi]

ans is D when temperature is increases and volume of the container is same pressure also increases