Gas Law Problems: Calculating Volume of 2.0g He at 25°C & 775 mm Pressure

[blackjack18]

what volume is occupied by 2.0 g of He at 25 degrees C and a pressure of 775 mm?

 

[Rake-MC]

$$Pv = nRT$$

P = pressure
v = volume
n = number of moles
R = universal gas constant
T = temperature.

Calculate how many moles are in 2.0 grams of helium, divide both sides of the equation by P.

Solve.

EDIT: Remember to have your units correct, IE Kelvin, kilograms etc

 

[blackjack18]

what is the constant? or is there one? if so, how do i determine what it is?

 

[Rake-MC]

R is the universal gas constant. It is always the same. In si units, it is: 8.314472 Joules per mol kelvin.

 

[blackjack18]

ok, I am not sure about this, but is the answer 1.59?

 

[Rake-MC]

What did you use as your numbers?

 

[blackjack18]

775=0.5(constant)(298), then divided by 775

 

[Rake-MC]

That equation is: $$p = nRT$$
You need volume on the left hand side to solve for it.
Also, you wrote in the question description that pressure = 775mm, I am going to assume that this is mmHg.
You are going to need to convert this to pascals.