Question

How many moles of gas does it take to occupy 150 L at a pressure of 4.2 atm and a temperature of 389 K?

A) 7.5 x 10⁻³ moles
B) 0.05 moles
C) 20 moles
D) 132 moles.

Answer 1

Using the Ideal Gas Law, the number of moles of gas that occupy 150 L at a pressure of 4.2 atm and a temperature of 389 K is calculated to be approximately 20 moles.

Step-by-step explanation:

To determine how many moles of gas are present in 150 L at a pressure of 4.2 atm and a temperature of 389 K, we can use the Ideal Gas Law equation PV=nRT, where P represents pressure, V represents volume, n represents the number of moles, R is the gas constant, and T is the temperature in kelvins.

R, the ideal gas constant, has different values depending on the units used for pressure. In this case, we will use the value of R that accommodates the pressure in atmospheres (atm), which is 0.0821 L atm mol⁻¹ K⁻¹. Rearranging the equation to solve for n (moles) gives us n = PV/RT. Plugging in the known values: n = (4.2 atm * 150 L) / (0.0821 L atm mol⁻¹ K⁻¹ * 389 K) results in n ≈ 19.98 moles, which rounds to 20 moles, giving us the answer choice C).