A flask contains 2.0 mol of He gas at 25°C and 1.00 atm. How much He gas, in grams, must be added to increase the pressure to 2.00 atm at constant temperature and volume?

Question

asked Aug 25, 2020 172k views

1 Answer

Hemant Singh · Answer 1 · 2020-08-30T02:04:25+0000

Answer:

Mass of He required = 8.0 g

Step-by-step explanation:

Given,

Initial moles of He = 2.0 mol

Initial pressure = 1.00 atm

final pressure = 2.00 atm

Ideal gas equation,

PV = nRT

As V, R and T are constant

So,
(P_1)/(P_2) =(n_1)/(n_2)

$(1.00 atm)/(2.00 atm) =(2.0)/(n_2)\\n_2=(2.0* 2.00)/(1.00) \\n_2=4.0 mol$

Molar mass of He = 4.00 g/mol

No. of moles of He needs to be added = 4.0 - 2.0 = 2.0 mol

Mass = No. of mole × Molar mass

= 2.0 × 4.0

= 8.0 g