A student combines a sample of gas (2.0 L) at 3.5 atm with with another gas (1.5 L) at 2.8 atm pressure into an empty 7.0 L flask. Assuming the gases are combined at constant temperature, what is the total gas pressure (in atmospheres) in the 7.0 L flask?

Total gas pressure is 1.60 atm

Explanation:

To solve this question we can use the Ideal Gases Law. We need to determine how many moles of each gas will be finally present at the flask of 7 L.

Let's asume the gas, are at Asbsolute T°, 273K

P. V = n . R . T

3.5 atm . 2L = n . 0.082 . 273K

(3.5 atm . 2L) / (0.082 . 273K) = 0.313 moles

(2.8 atm . 1.5L) / (0.082 . 273K) =  0.188 moles

Total moles = 0.313 mol + 0.188 mol = 0.501 mol

Let's calcualte the hole pressure

P . 7L = 0.501 moles . 0.082 . 273K

P = (0.501 moles . 0.082 . 273K) / 7L → 1.60 atm