Question

1g of helium gas is confined in a two-litre flask under a pressure of 2.05 atm. What is its temperature?

Answer 1

To solve the given illustration we only need basic information about the ideal gas law and its equation. Knowing the basics of the ideal gas equation, we can easily solve this equation.
The equation of ideal gas i.e. $PV=nRT$ needs to be analysed to solve a given problem; and amazingly we only need this single equation.

Complete answer:
Let us study the ideal gas equation before moving towards the given illustration;
Ideal gas equation-
An ideal gas is a hypothetical gas following all general laws such as Boyle’s law and Charles law which then forms the universally acceptable ideal gas equation i.e.
$PV=nRT$
where,
P = pressure of an ideal gas
V = volume of an ideal gas
n = the amount of ideal gas measured in terms of moles
R = universal gas constant
T = temperature
So, for given illustration,
Given data,
P = 2.05 atm
V = 2L
R = $0.0821Latm{{K}^{-1}}mo{{l}^{-1}}$
Given mass of He = 1 g
As, we know the atomic mass of He = 4 g/mol
Thus, n = $\dfrac{1g}{4g/mol}=0.25mol$
Now, putting all the values in the general ideal gas equation we get,
$\begin{aligned} & T=\dfrac{PV}{nR} \\\ & T=\dfrac{2.05\times 2}{0.25\times 0.0821} \\\ & T=199.75K \\\ \end{aligned}$
Therefore, the temperature is 199.75 K.

Note:
This is a general problem based on ideal gas laws and equations. Do note to analyse units properly before solving the illustration.