Chemistry Help!

Question

What is the temperature in K of 0.0420 mole of gas at 16.3 psi and that occupies 981 mL?

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A 0.56 g sample of gas is contained in 250.0 mL cylinder. Its pressure is 983 mmHg and its temperature is 22.7 oC. What is the molar mass of the gas?

Answer 1

I will set this up for you, and you can work it in the appropriate units.

Assuming it is an ideal gas, it obeys the equation of state:

PV = nRT

 

P = pressure
V = volume
T = absolute temperature
R = universal gas constant
n = number of moles = mass / (molecular weight) = m/W
m = mass
W = molecular weight

 

First part:

 

PV = nRT ⇒ T = PV / (nR)

 

You are given P, V, and n.  Get R from tables.  Work in appropriate units, and substitute.  Can you finish from here?

 

Second part:

 

I will set this up for you, and you can work it in the appropriate units.

 

Assuming it is an ideal gas, it obeys the equation of state:

 

PV = nRT

 

PV = (m/W)RT

 

W = mRT / (PV)

 

You are given m, T, P, and V.  You can find R in your chemistry book.  Convert T to the Kelvin scale, since the relation is valid only for absolute temperature.  Be careful with units.  Can you finish from here?