Final answer:
The volume of 0.4 mol of H₂ gas at 20°C and 2 atm is 5 L, using the Ideal Gas Law with the temperature converted to Kelvin and using the appropriate value for the gas constant.
Step-by-step explanation:
To determine the volume of 0.4 mol of H₂ gas at 20°C and 2 atm, we can use the Ideal Gas Law, which is given by PV = nRT. Here, P is the pressure of the gas, V is its volume, n is the number of moles, R is the gas constant, and T is the temperature in Kelvin. The value of R when using SI units is 0.0821 L·atm/K·mol. First, we need to convert the temperature to Kelvin by adding 273.15 to the Celsius temperature, which gives us T = 293.15 K.
Using the Ideal Gas Law, we can solve for V (volume) as follows:
V = × nRT/P
V = × (0.4 mol) × (0.0821 L·atm/K·mol) × (293.15 K) / (2 atm)
When we carry out the calculation, we get V = 4.83 L, which is rounded to 5 L. Therefore, option C (5 L) is the correct answer.