Question

Question #d111e

Answer 1

The boiling point is 102.86 °C.

Explanation:

We use the boiling point elevation expression

`ΔT_b = iK_bm`

where

• `ΔT_b` = change in boiling point;
• `i` is the van’t Hoff factor;
• `K_b` is the molal boiling point elevation constant for the solvent;
• `m` is the molality of the solute.

Step 1. Calculate the `i` value.

`"MgCl"_2("s") → "Mg"^(2+)("aq") + "2C"l⁻("aq")`

Since 1 mol of `"MgCl"_2` forms 3 mol of ions, `i = 3`.

Step 2. Calculate `ΔT_b`.

For water, `K_b = "0.512 °C·kg·mol"^-1`

`ΔT_b = iK_bm = "3 × 0.512 °C·kg·mol"^-1 × "1.86 mol·kg"^-1 = "2.86 °C"`

Step 3.

`T_b = T_b° + ΔT_b = "(100.00 + 2.86) °C" = "102.86 °C"`

Here's a video on calculating a boiling point.