Question

What mass of water must be used to prepare a solution of 25.5 g of CaCl2 dissolved in water if the mole fraction

of the CaCl2 in solution is 0.105?

​

Answer 1

Answer:

According to Van't Hoff's equation, the osmotic pressure

Π=iCRT=

V

in

B

RT

.

Here, i is the Van't Hoff's factor, C is the molar concentration, R is the ideal gas constant, T is temperature, nB is the number of moles of calcium chloride and V is the volume of the solution.

Now we have given below values:

π = 0.75 atm

V = 2.5L

i = 2.47

T = (27+273) K = 300K

and R = 0.0821L atm k

−1

mol

−1

0.75=

2.5

2.47×n

B

×0.0821×300

n

B

=0.0308 mol

The molar mass of calcium chloride is 111 g/mol.

Amount of calcium chloride dissolved =0.0308×111=3.42 g. iss q pr syd bn jaye