Answer:
145.78g/mol
Explanation:
Let the time taken for the two gas to effuse be x
For O2:
Volume = 6.51mL
Time = x
Rate (R1) = volume/time
R1 = 6.51/x
For the unknown gas:
Volume = 3.05mL
Time = x
Rate (R2) = Volume/time
R2 = 3.05/x
Now, we can obtain the molar mass of the unknown gas as follows:
R1 = 6.51/x
M1 (O2) = 16 x 2 = 32g/mol
R2 = 3.05/x
M2(unknown gas)
R1/R2 = √(M2/M1)
(6.51/x)/(3.05/x) = √(M2/32)
6.51/3.05 = √(M2/32)
Take the square of both side
(6.51/3.05)^2 = M2/32
Cross multiply to express in linear form:
M2 = (6.51/3.05)^2 x 32
M2 = 145.78
Therefore, the molar mass of the unknown gas is 145.78g/mol