Question

A helium balloon, which originally contained 0.40 moles of helium, lost 10. percent of its volume. Assume that the temperature and pressure stay constant. How many grams of helium escaped from the balloon? Report your answer with two significant figures.

Answer 1

According to Avagadro's law :

Volume of helium gas is directly proportional to the amount of gas at constant temperature and pressure

V1/n1 = V2/n2

V1 total volume = 100 %, V2 volume of gas escaped= 10%

n1, total number of gas moles = 0.4 moles

n2, number of moles of helium gas escaped = n moles

100%/0.4 moles = 10%/n moles

10/0.4 = 1/n

n = 0.4/10 = 0.04 moles

Molar mass of helium = 4 gm/mol

Number of helium gas lost n = 0.04 moles = amount of gas lost/molar mass = x gm/4 gm/mol

0.04 moles × 4 g/mol = x = 0.16 gms

Amount of helium gas escaped = 0.16 gms