# Asolution is made by dissolving 14.0g of potassium chloride to a final volume of 78.9mL solution. What is the weight /volume % of the solute?

Jul 22, 2016

17.7%

#### Explanation:

The thing to remember about a solution's mass by volume percent concentration, $\text{m/v %}$, is that it is calculated by taking the number of grams of solute present in $\text{100 mL}$ of solution.

This implies that you can find a solution's mass by volume percent concentration by determining how many grams of solute you get in $\text{100 mL}$ of solution.

$\textcolor{b l u e}{| \overline{\underline{\textcolor{w h i t e}{\frac{a}{a}} \text{% m/v" = "no. of grams of solute / 100 mL solution} \textcolor{w h i t e}{\frac{a}{a}} |}}}$

Now, you know that your solution is made by dissolving $\text{14.0 g}$ of potassium chloride, $\text{KCl}$, which constitutes your solute, in enough water to make the final volume of the solution equal to $\text{78.9 mL}$.

You can use this information as a conversion factor to calculate the number of grams of potassium chloride present in $\text{100 mL}$ of solution

100 color(red)(cancel(color(black)("mL solution"))) * overbrace("14.0 g KCl"/(78.9color(red)(cancel(color(black)("mL solution")))))^(color(blue)("given by the problem")) = "17.744 g KCl"

Since this is how many grams of solute you get in $\text{100 mL}$ of solution, you can say that the solution has a mass by volume percent concentration equal to -- don't forget to add the percent symbol, %.

"% m/v" = color(green)(|bar(ul(color(white)(a/a)color(black)("17.7% KCl")color(white)(a/a)|)))

The answer is rounded to three sig figs.