The ideal gas law is PV = nRT
where n is the moles and R is the gas constant.
We are told that neither the temperature or pressure change. Just the moles and volume.
The initial condition is P1V1 = n1RT1
The final is: P2V2 = n2RT2
But P1 = P2 and T1 = T2. The R is a constant.
Divide one equation by the other and cross out the R, T and P, since they are equal. We wind up with this:
V1/V2 = n1/n2
The only unknown is V2, so rearrange and enter the data:
V2 =V1(n2/n1)
V2 = 0.50L * (n2/0.10)
n2 need the total number of moles. They gave us the starting amount in moles, but the added helium is in grams. Convert the 0,63 g of helium into moles by dividing by helium's molar mass (4g/mole). Add that to the initial 0,10 mole and solve the equation. Since n2 goes up, the volume goes up, as we would expect under the conditions that neither pressure nor temperature change. Therefore, the volume must go up.
Bob
