Answer
a. Mass/volume percent(m/v) = $6.25 \%$ (m/v) $LiCl$ solution
b. Mass/volume percent(m/v) = $6.3 \%$ (m/v) $casein$ solution
Work Step by Step
a.
1. Write the expression for the mass/volume percent:
$$Mass/volume \space percent(m/v) = \frac{grams \space of \space solute}{mL \space of \space solution} \times 100\%$$
$$Mass/volume \space percent(m/v) = \frac{ 2.50 \space g \space LiCl }{ 40.0 \space mL \space LiCl \space solution} \times 100\%$$
Mass/volume percent(m/v) = $6.25 \%$ (m/v) $LiCl$ solution
b.
1. Write the expression for the mass/volume percent:
$$Mass/volume \space percent(m/v) = \frac{grams \space of \space solute}{mL \space of \space solution} \times 100\%$$
$$Mass/volume \space percent(m/v) = \frac{ 7.5 \space g \space casein }{ 120 \space mL \space low-fat \space milk} \times 100\%$$
Mass/volume percent(m/v) = $6.3 \%$ (m/v) $casein$ solution