Question

Calculate the mole fraction of KI in a solution made by dissolving 3.4 g of KI in 5.8 g of water. (Step by step)

A. 0.060
B. 0.064
C. 0.37
D. 0.59
E. 6.4

Answer 1

The correct answer is 0.058

Explanation:

The mole fraction of KI (X) in the solution is the number of moles of KI divided into the total number of moles of the solution (nt):

X= moles KI/nt

First we have to calculate the molecular weights of the components of the solution: KI and water (H₂O):

Molecular weight (Mw) of KI:

Mw(KI)= 39 g/mol + 127 g/mol = 166 g/mol

Molecular weight of H₂O:

Mw(H₂O)= (1 g/mol x 2) + 16 g/mol = 18 g/mol

Then, we calculate the number of moles there is of each component in the solution by dividing the mass into Mw:

Moles of KI= mass KI/Mw(KI) = 3.4 g/166 g/mol = 0.020 mol KI

Moles of H₂O= mass H₂O/Mw(H₂O)= 5.8 g/18 g/mol = 0.322 mol H₂O

Thus, the total moles of solution will be:

nt= moles KI + moles H₂O= 0.020 mol + 0.322 mol = 0.342 mol

Finally, we divide the moles of KI into the total moles of solution (nt) to obtain the mole fraction (X):

X= moles KI/nt = 0.020 mol/0.342 mol = 0.058