We will use the expression for freezing point depression ∆Tf
∆Tf = i Kf m
Since we know that the freezing point of water is 0 degree Celsius, temperature change ∆Tf is
∆Tf = 0C - (-3°C) = 3°C
and the van't Hoff Factor i is approximately equal to 2 since one molecule of KCl in aqueous solution will produce one K+ ion and one Cl- ion:
KCl → K+ + Cl-
Therefore, the molality m of the solution can be calculated as
3 = 2 * 1.86 * m
m = 3 / (2 * 1.86)
m = 0.80 molal

4 0

3 years ago

A sample of Element X is found to contain 67.25% of isotope type 1 (85.91) and 32.75% of isotope type 2 (87.91). Calculate the a

KengaRu [80]

Answer:

The average atomic mass is 86.565

Explanation:

An element's average atomic mass is the sum of the products of the masses of the isotopes of the element and their percentage abundance divided by 100

The average atomic mass of the Element X is given as follows;

Isotope type 1 (85.91) ×

Isotope ${}$ Abundance (%) Mass /100 Portion of average mass

Type 1 ${}$ 67.25 × 85.91 ÷ 100 57.774475

Type 2 ${}$ 32.75 × 87.91 ÷ 100 28.790525

${}$ Average atomic mass = 86.565

The average atomic mass = 86.565.

5 0

3 years ago