# Question #5174b

Apr 12, 2017

The mass will be 4429 g

#### Explanation:

Use the ideal gas law to solve this problem: $P V = n R T$

This law specifies the possible conditions for a sample of gas, and makes it possible for us to find a fourth condition when values are given for the other three.

Here, we know the pressure, P is 135.0 atm. The volume, V is 200.0 L and the temperaure T is 24.00 °C, or better as 297K.

Thus, we can solve for the missing value, which is $n$, the gas quantity in moles.

$n = \frac{P V}{R T}$

You must be careful to choose a value for the gas constant $R$ that matches the units given in the problem. Specifically, since the pressure is in atmospheres, we use $R = 0.0821 \left(\text{L atm")/(K" mol}\right)$

$n = \frac{\left(135\right) \left(200\right)}{\left(0.0821\right) \left(297\right)} = 1107.3$ moles

Now, multiply by the molar mass of helium (4 g) and this answer is reported as a mass.