[positiveion]

Seperate samples of 2 gases, each containing a pure substance, are found to have the same density under the same conditions of temperature and pressure. Which statement about these 2 samples must be correct?

a. same volume
b. same RAM
c. equal no. moles of gas in the 2 samples
d. they condense at the same temperature

the answer is b

and i understand how the answer was achieved

m/v needs to be the same but m and v do not necessarily need to be the same

HOWEVER, what I don't understand is this equation that wel earnt:

p1v1/t1 = p2v2/t2

i don't understand how the above equation can even APPLY because according to THIS equation if p1 and t1 are the same then v1 has to be the same too otherwise the ratio will be out of whack and p1v1/t1 will NOT equal p2v2/t2.

so i am a bit confused about that. can anyone help me pelase?

thank you very much

[AWK]

pV=mRT/M
=>
pM/(RT)=d

[positiveion]

I understand that! What I don't understand is how

P1v1/t1 = P2V2/T2

can be a valid equation since it cannot apply to this situation

[Borek]

how

P1v1/t1 = P2V2/T2

can be a valid equation since it cannot apply to this situation

Why it can't apply?

[positiveion]

because if

p1 and t1 are equal and p2 and t2 are equal in the equation

p1v1/t1 = p2v2/t2

then v1 and v2 have to be equal too otherwise the equation won't work

[sjb]

What actually is the ideal gas equation, in full?

[Borek]

then v1 and v2 have to be equal too otherwise the equation won't work

So perhaps they are equal?

Note, that p₁v₁/t₁ = p₂v₂/t₂ is not absolutely universal, there is an important restriction put on the system it describes. Think about sjb question.

[thatspuru]

The problem here is that you can't apply that equation unless the number of moles are same too. You'd have to consider n1 and n2 too.