Question

On adding 1 g arsenic to 80 g benzene, the freezing
point of benzene is lowered by 0.19°C. The
formula of arsenic is (K, = 5.08 K kg mol-').​

Answer 1

Answer:

g of arsenic dissolved in 86 g of benzene brings down the freezing point to

from

.If

of benzene is

, the atomicity of the molecule is : (As =75 or As GAM 75)

Answer 2

Answer:

The formula of arsenic is As₄.

Explanation:

Given:

ΔTf = 0.19°c

Kf = 5.08 K kg/mol

The depression in the freezing point depends on the concentration of the solute in a solution and is related to molality as below.

ΔTf = i × Kf × molality

where Tf is the lowering in freezing point;

i is the Van't Hoff factor and

Kf is the molal depression constant or cryoscopic constant.

Substituting the values in the above equation.

0.19 = i×5.08×(1000×1/80×75)        

       = i×5.08 × 12.5/75

i = 0.22

α = (i-1)/(1/n-1) = 1

α is the degree of association.

i-1   =  1/n - 1

i     =  1/n

n    =  1/i

     =  4.4

The formula of arsenic is As₄.

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