Question #cb5de
1 Answer
Explanation:
In order to find the mole fraction of potassium chloride,
To do that, you must pick a sample of this solution and calculate how many grams of potassium chloride, the solute, and how many grams of water, the solvent, it contains.
The problem provides you with the mass by mass percent concentration,
In this case, a
This means that if you pick a
m_"KCl" = "23.3 g"mKCl=23.3 g
and
m_"water" = "100.0 g" - "23.3 g" = "76.7 g water"mwater=100.0 g−23.3 g=76.7 g water
To convert these masses into moles, use the molar masses of the two compounds
23.3 color(red)(cancel(color(black)("g"))) * "1 mole KCl"/(74.55 color(red)(cancel(color(black)("g")))) = "0.31254 moles KCl"
76.7 color(red)(cancel(color(black)("g"))) * ("1 mole H"_2"O")/(18.015color(red)(cancel(color(black)("g")))) = "4.25756 moles H"_2"O"
The mole fraction of potassium chloride,
You will thus have
chi_"KCl" = (0.31254 color(red)(cancel(color(black)("moles"))))/((0.31254 + 4.25768)color(red)(cancel(color(black)("moles")))) = color(green)(|bar(ul(color(white)(a/a)color(black)(0.0684)color(white)(a/a)|)))
The answer is rounded to three sig figs.