103k views
5 votes
I NEED HELP ASAP!!!

Question 13
A sample of helium has a volume of 25 L at STP. How many moles of helium is this?
I

User Brother
by
7.9k points

1 Answer

5 votes

Step-by-step explanation:

To answer this question, we'll need to use the Ideal Gas Law:

p

V

=

n

R

T

,

where

p

is pressure,

V

is volume,

n

is the number of moles

R

is the gas constant, and

T

is temperature in Kelvin.

The question already gives us the values for

p

and

T

, because helium is at STP. This means that temperature is

273.15 K

and pressure is

1 atm

.

We also already know the gas constant. In our case, we'll use the value of

0.08206 L atm/K mol

since these units fit the units of our given values the best.

We can find the value for

n

by dividing the mass of helium gas by its molar mass:

n

=

number of moles

=

mass of sample

molar mass

=

6.00 g

4.00 g/mol

=

1.50 mol

Now, we can just plug all of these values in and solve for

V

:

p

V

=

n

R

T

V

=

n

R

T

p

=

1.50 mol

×

0.08206 L atm/K mol

×

273.15 K

1 atm

= 33.6 L

this is not the answer but it will help you

do by the formula it is on the answer

User Peritus
by
7.3k points