Question

Question #e3ea3

Answer 1

(d) `101.5^oC`

Explanation:

We can automatically eliminate options (a) and (b), because one of the colligative properties of solutions is boiling-point elevation, meaning the boiling point will have increased (i.e. greater than `100.0 ^oC`).

The equation for calculating boiling-point elevation is

`DeltaT_"b" = i * K_"b" * m`

where `DeltaT_"b"` is the change in boiling point,
`i` is called the van't Hoff factor, which for these purposes is essentially the number of dissolved species in one unit of solute (equal to `2` for `"NaCl"`),
`K_"b"` is the molal boiling-point constant for water, which is given, and
`m` is the molality of the solution.

Plugging in our known variables, we have

`DeltaT_"b" = (2)(0.512( "^oC)/cancel(m))(1.5cancel(m)) = 1.5 ^oC`

To find the new boiling point, simply add this to the boiling point of water, `100 ^oC`:

`100 ^oC + 1.5 ^oC = color(red)(101.5 ^oC`

So option (d) is the correct answer.