Sample Problem 5.4
Applying the Volume-Amount Relationship
PROBLEM:
A scale model of a blimp rises when it is filled with helium to a volume of 55 dm3 (V2). When 1.10 mol of He (n1) are added to the blimp, the volume is 26.2 dm3 (V1). How many more grams of He must be added to make it rise? Assume constant T and P.
PLAN:
SOLUTION:
We are given the initial n1 and V1 and the final V2. We need to find n2 and convert it from moles to grams.
n1(mol) of He
n2(mol) of He
mol to be added
g He to add
x V2 / V1
x M
subtract n1
n1 = 1.10 mol
n2 = unknown
V1 = 26.2 dm3
V2 = 55.0 dm3
P and T are constant
= 2.31 mol
= 4.84 g He
or
x
2.31 mol - 1.10 mol = 1.21 mol x
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