Assuming constant pressure and temperature, how many moles of gas have been added to the initial 3 moles of gas when the volume increases from 2.0 to 4.0 liters?

1.5 moles

2 moles

3 moles

6 moles

We first assume that the gas is ideal which is a safe assumption to approximate the answer to the problem. Then we need to know the ideal gas equation and that is:

PV=nRT

where

P - pressure

V - volume

n-number of moles-

R - ideal gas constant

T-temperature.

Since we know that P, T and V are constant, rearranging the equation would lead to:

P/TR = n/V or the ratio of the moles of gas and volume is constant.

(3moles) / 2L = (3+x) / 4L

where

x is the additional moles.

Solving for x = 3 moles.