Question

Determine the change in boiling point for 397.7 g of carbon disulfide (Kb = 2.34°C kg/mol) if 35.0 g of a nonvolatile, nonionizing compound is dissolved in it. The molar mass of the compound is 70.0 g/mol and the boiling point of the pure carbon disulfide is 46.2°C.

Answer 1

Answer: The change in boiling point for 397.7 g of carbon disulfide (Kb = 2.34°C kg/mol) if 35.0 g of a nonvolatile, nonionizing compound is dissolved in it is
`2.9^0C`

Step-by-step explanation:

Elevation in boiling point:

`T_b-T^o_b=i* k_b* (w_2* 1000)/(M_2* w_1)`

where,

`T_b` = boiling point of solution = ?

`T^o_b` = boiling point of pure carbon disulfide=
`46.2^oC`

`k_b` = boiling point constant =
`2.34^0Ckg/mol`

m = molality

i = Van't Hoff factor = 1 (for non-electrolyte)

`w_2` = mass of solute = 35.0 g

`w_1` = mass of solvent (carbon disulphide) = 397.7 g

`M_2` = molar mass of solute = 70.0 g/mol

Now put all the given values in the above formula, we get:

`(T_b-46.2)^oC=1* (2.34^oC/m)* ((35.0g)* 1000)/(70.0* (397.7g))`

`T_b=49.1^0C`

Therefore, the change in boiling point is
`(49.1-46.2)^oC=2.9^0C`