Question

18.8 grams of gas occupies 14.5 L at 79.9 kPa at 30.0 Celsius degree. What is It’s molecular weight?(grams /moles)

Answer 1

Answer : The molecular weight of gas is, 40.9 g/mol

Explanation :

To calculate the molecular weight of gas we are using ideal gas equation:

`PV=nRT\\\\PV=(w)/(M)RT`

where,

P = pressure of gas = 79.9 kPa

V = volume of gas = 14.5 L

T = temperature of gas =
`30.0^oC=273+30.0=303K`

R = gas constant = 8.314 L.kPa/mole.K

w = mass of gas = 18.8 g

M = molecular weight of gas = ?

Now put all the given values in the ideal gas equation, we get:

`(79.9kPa)* (14.5L)=(18.8g)/(M)* (8.314L.kPa/mole.K)* (303K)`

`M=40.9g/mol`

Therefore, the molecular weight of gas is, 40.9 g/mol