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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Fish200398 on March 29, 2020, 12:16:50 PM

Title: Finding partial pressure
Post by: Fish200398 on March 29, 2020, 12:16:50 PM

We have 22.4 L at STP gas mixture of He and N2.
The weight of this gas mixture is 8.8 g
What is partial pressure of He (in Pa) ?

I found the answer but not sure
So :
 22.4 L gas at STP will contains 1 mole of the gas
Mole He + mole H2 = 1 mole
A + B = 1 mole

Mass He + mass N2 = 8.8 g
A .MrHe + B .MrN2 = 8.8 g
2 g/mole A + 28 g/mole B = 8.8 g
2A + 28B = 8.8 moles

26 B = 6.8 moles
B = 68/260 = 34/130 moles
A = 96/130 moles

At STP , pressure is 1 atm, means the gas mixture has 1 atm pressure or 101,325 Pa.

Partial pressure of He =
 ( mole He/total mole ) × total pressure
= ( 96/130 ) × 101,325 Pa
= 74,824 Pa

Is it true?

The answer 80,000 Pa though

Title: Re: Finding partial pressure
Post by: AWK on March 29, 2020, 12:59:39 PM

Quote from: Helly on March 29, 2020, 12:16:50 PM

We have 22.4 L at STP gas mixture of He and N2.
The weight of this gas mixture is 8.8 g
What is partial pressure of He (in Pa) ?

I found the answer but not sure
So :
 22.4 L gas at STP will contains 1 mole of the gas
Mole He + mole H2 = 1 mole
A + B = 1 mole

Mass He + mass N2 = 8.8 g
A .MrHe + B .MrN2 = 8.8 g
2 g/mole A + 28 g/mole B = 8.8 g
2A + 28B = 8.8 moles

26 B = 6.8 moles
B = 68/260 = 34/130 moles
A = 96/130 moles

At STP , pressure is 1 atm, means the gas mixture has 1 atm pressure or 101,325 Pa.

Partial pressure of He =
 ( mole He/total mole ) × total pressure
= ( 96/130 ) × 101,325 Pa
= 74,824 Pa

Is it true?

The answer 80,000 Pa though

It cannot be true

Title: Re: Finding partial pressure
Post by: Fish200398 on March 29, 2020, 02:13:32 PM

Quote from: Helly on March 29, 2020, 12:16:50 PM

We have 22.4 L at STP gas mixture of He and N2.
The weight of this gas mixture is 8.8 g
What is partial pressure of He (in Pa) ?

I found the answer but not sure
So :
 22.4 L gas at STP will contains 1 mole of the gas
Mole He + mole N2 = 1 mole
A + B = 1 mole

Mass He + mass N2 = 8.8 g
A .MrHe + B .MrN2 = 8.8 g
4 g/mole A + 28 g/mole B = 8.8 g
4A + 28B = 8.8 moles

24 B = 4.8 moles
B = 48/240 = 0.2 moles
A = 0.8 moles

At STP , pressure is 1 atm, means the gas mixture has 1 atm pressure or 101,325 Pa.

Partial pressure of He =
 ( mole He/total mole ) × total pressure
= 0.8 × 101,325 Pa
= 81,060 Pa

Thank you