What is the final volume, in liters, when each of the following changes occurs in the quantity of the gas at constant pressure and temperature?

Question

A sample containing 4.20 g of O2 gas has an initial volume of 14.5 L .

A sample of 0.800 mole of O2 is added to the 4.20 g of O2 in the container.

Express the volume in liters to three significant figures.

A sample of 1.50 g of O2 is removed from the 4.20 g of O2 in the container.

Express the volume in liters to three significant figures.

A sample of 3.00 g of O2 is added to the 4.20 g of O2 gas in the container.

Express the volume in liters to three significant figures.

Answer 1

V1 = initial volume = 14.5 L

n1 = initial moles of gas = 4.20 g O2 x 1 mol O2 / 32 g = 0.13125 moles O2

V2 = final volume = ?

n2 = final moles of gas = 0.13125 mol + 0.800 mol = 0.93125 moles

V1/n1 = V2/n2 and solving for V2, we have...

V2 = V1n2 / n1 = 14.5 L x 0.93125 / 0.13125

V2 = 102.88 L = 103 L (3 sig. figs.)

The other problem can be done in a similar fashion but you will be removing 1.50 g of O2 (convert to moles). Subtract this number of moles from 0.13125 mol O2 and plug into the equation to solve for V2

Try the third one yourself and if you have a problem, submit it again, but include your attempt and where you are having a problem.