Q. 9.33 - An Introduction to General, Organic, and Biological Chemistry

Question

Calculate the mass percent $(m/m)$ for the solute in each of the following:

a. $25 g of KCl$ and $125 g of H_{2}O$

b. $12 g$ of sucrose and $225 g$ of tea solution.

c. $8.0 g of CaC{l}_2$ and $80.0 g of CaC{O}_2$ solution.

Step-by-Step Solution

Answer

(part a) Mass percent for $25 g of KCl$ and $125 g of H_{2}O$ is $17\% (\mathrm{m}/\mathrm{m}) \mathrm{KCl}$

(part b) Mass percent for $12 g$ of sucrose and $225 g$ of tea solution is $5.3\% (\mathrm{m}/\mathrm{m}) {\mathrm{CaCl}}_2$

(part c) Mass percent for $8.0 g of CaC{l}_2$ and  solution is $10\% (\mathrm{m}/\mathrm{m}) \mathrm{sucrose}$

Step 1: Given Information (part a).

Given:

$25 g of KCl$

$125 g of H_{2}O$

Step 2: Explanation (part a).

The term "mass percent" refers to the number of grammes of solute dissolved in $100 g$ of solution.

$$\begin{gathered} \text{ Mass of solution }\left(\mathrm{g}\right)=\text{ Mass of solute }\left(\mathrm{g}\right)+\text{ Mass of solvent }\left(\mathrm{g}\right) \\ =25 g+125 g \\ =150 g \end{gathered}$$

Mass percent equation is,

$\text{ Mass percent }(\mathrm{m}/\mathrm{m})=\frac{\text{ Mass of solute }\left(\mathrm{g}\right)}{\text{ Mass of solution }\left(\mathrm{g}\right)}\times 100\mathrm{\%}\text{. }$

Substitute the values,

$$\begin{gathered} \text{ Mass percent }(\mathrm{m}/\mathrm{m})=\frac{25\mathrm{gKCl}}{150\mathrm{g}}\times 100\mathrm{\%} \\ =17\% (\mathrm{m}/\mathrm{m}) \mathrm{KCl} \end{gathered}$$

Step 3: Given Information (part b).

Given:

$12 g$ of sucrose.

$225 g$ of tea solution.

Step 4: Explanation (part b).

Mass percent equation is,

$\mathrm{Mass} \mathrm{percent} (\mathrm{m}/\mathrm{m})=\frac{\text{ Mass of solute }\left(\mathrm{g}\right)}{\text{ Mass of solution }\left(\mathrm{g}\right)}\times 100\mathrm{\%}\text{. }$

Substitute the values,

$$\begin{gathered} \text{ Mass percent }(\mathrm{m}/\mathrm{m})=\frac{8.0\mathrm{g}{\mathrm{CaCl}}_2}{80.0g \mathrm{of} {\mathrm{CaCO}}_3}\times 100\mathrm{\%} \\ =10\% (\mathrm{m}/\mathrm{m}) {\mathrm{CaCl}}_2 \end{gathered}$$

Step 5: Given Information (part c).

Given:

$8.0 g of CaC{l}_2$

$80.0 g of CaC{O}_2$ solution.

Step 6: Explanation (part c).

The mass percent equation is,

$\mathrm{Mass} \mathrm{percent} (\mathrm{m}/\mathrm{m})=\frac{\text{ Mass of solute }\left(\mathrm{g}\right)}{\text{ Mass of solution }\left(\mathrm{g}\right)}\times 100\mathrm{\%}\text{. }$

Substitute the values,

$$\begin{gathered} \text{ Mass percent }(\mathrm{m}/\mathrm{m})=\frac{12g\text{ sucrose }}{225\mathrm{g}}\times 100\mathrm{\%} \\ =5.3\% (\mathrm{m}/\mathrm{m}) \mathrm{sucrose} \end{gathered}$$