A solution is made by dissolving 3.60g of sodium chloride to a final volume of 115mL solution. What is the weight/volume % of the solute?

Question

Caleb Adams · Accepted Answer

#3.13%#

The idea here is that a solution's mass by volume percent concentration, #"% m/v"#, sometimes called weight by volume, tells you how many grams of solute you get per #"100 mL"# of solution.

#color(blue)(|bar(ul(color(white)(a/a)"% m/v" = "grams of solute"/"100 mL of solution" xx 100 color(white)(a/a)|)))#

This means that in order to determine a solution's mass by volume percent concentration, all you have to do is figure out how many grams of solute you have in #"100 mL"# of solution.

In your case, you know that you're dissolving #"3.60 g"# of sodium chloride, #"NaCl"#, which is your solute, to get a final volume of #"115 mL"# of solution.

Right from the start, you can say that the solution's mass by volume percent concentration will be lower than #3.60%# because #"100 mL"# will contain less than #"360 g"# of sodium chloride.

More specifically, #"100 mL"# of solution will contain

#100 color(red)(cancel(color(black)("mL solution"))) * "3.60 g NaCl"/(115color(red)(cancel(color(black)("mL solution")))) = "3.13 g NaCl"#

So, if #"100 mL"# of solution contain #"3.13 g"# of solute, it follows that the solution's #"% m/v"# will be

#color(green)(|bar(ul(color(white)(a/a)color(black)("% m/v " = " 3.13 %")color(white)(a/a)|)))#

The answer is rounded to three sig figs.

Natalie Anton · Answer

undefined To calculate the weight/volume % of the solute, divide the mass of the solute (3.60g) by the volume of the solution (115mL) and then multiply by 100.

$$ \text{Weight/volume \%} = \frac{\text{Mass of solute (g)}}{\text{Volume of solution (mL)}} \times 100 $$

$$ \text{Weight/volume \%} = \frac{3.60g}{115mL} \times 100 = 3.13\% $$