Question

Give reasons when 2gm of benzoic acid is dissolved in 25gm of benzene the experimentaaly determined molar mass is alwz grater than the true value

Answer 1

ANSWER:

First we take

W=2kg    k=4.9 kg/mol

w1=25g   ΔTf=1.62k

substituting this in the equation.

Δt=(k*w2*1000)/m2*w1

m2=241.98 g/mol

eperimental molar mass of benzoic acid=241.98 g/mol

now we need consider.

2 C6H5COOH---->(C6H5C00H)2

X represents the degree of association of solute the (1-x) mol of bezoic left and x/2.

1-x+x/2 = 1-x/2 .

i= normal molecular mass/abnormal molecular mass

x/2=1-122/241.98

x=2*0.496 =0.992

so the degree of association is 99.2%