What volume is occupied by 0.34 moles of Helium gas?

I will assume that you mean

STP (Standard Temperature and Pressure)

21

3

≈

7 L

Explanation:

Since we know that

1 mole

of an ideal gas occupies

22.4 L

at

STP

then can establish the following relationships:

22.4 L

1 mole

or

1 mole

22.4 L

Knowing that, we can solve for the volume occupied by the helium gas,

0.35

mole

1

⋅

22.4 L

1

mole

=

7.84 L

as

7.84 L

−

−

−

−

−

The answer makes sense because if

1 mole

occupies

22.4 L

, then

0.35 moles

(roughly a third of the moles) will occupy a third of

22.4 L

(

if we round down 22.4 L to 21 L

)

−

−

−

21

3

≈

7 L

the answer would be a