Question

A hydrogen halide diffuses 1.49 times faster than HBr. This hydrogen halide is

Answer 1

To solve this problem, we must assume ideal gas behaviour so that we can use Graham’s law:

vA / vB = sqrt (MW_B / MW_A)

where,

vA = speed of diffusion of A  (HBR)

vB = speed of diffusion of B (unknown)

MW_B = molecular weight of B (unkown)

MW_A = molar weight of HBr = 80.91 amu

 

We know from the given that:

vA / vB = 1 / 1.49

 

So,

1/1.49 = sqrt (MW_B / 80.91)

MW_B = 36.44 g/mol

 

Since this unknown is also hydrogen halide, therefore this must be in the form of HX.

HX = 36.44 g/mol , therefore:

x = 35.44 g/mol

 

From the Periodic Table, Chlorine (Cl) has a molar mass of 35.44 g/mol. Therefore the hydrogen halide is:

HCl