Question

What is the formal concentration (expressed as $\mathrm{mol}/\mathrm{L}=\mathrm{M}$) ofNaCI when 32.0gare dissolved in water and diluted to 0.500L?

Short answer

The value of the formula concentration is 1.10mol/L

Step-by-step solution

Definition of formal concentration

When a material's concentration is measured as the number of moles of the substance contained in a litre of solution, it is called a formal concentration.

Given values

A molarity of some strong electrolyte is described as the F (formal concentration). We have 32.0 g of NaCl dissolved in water and diluted to0.500 in this scenario.

The given mass of $=\mathbf{32}\mathbf{.}\mathbf{0}\mathrm{g}$

The volume$=\mathbf{0}\mathbf{.}\mathbf{500}\mathrm{L}$

The molar mass $\mathbf{58}\mathbf{.}\mathbf{44}\mathrm{g}/\mathrm{mol}$

Find the value of concentration

Use the formula below to get the number of moles:

$$\begin{gathered} \mathrm{n}\left(\mathrm{NaCI}\right)=\frac{\mathrm{m}}{\mathrm{N}} \\ =\frac{\mathbf{32}\mathrm{g}}{\mathbf{58}\mathbf{.}\mathbf{44}\mathrm{g}/\mathrm{mol}} \\ =\mathbf{0}\mathbf{.}\mathbf{547}\mathrm{mol} \end{gathered}$$

Represent this number as a formal concentration of a solution $\left(\mathrm{mol}/\mathrm{L}=\mathrm{M}\right)$:

$$\begin{gathered} \mathrm{c}=\frac{\mathrm{n}}{\mathrm{V}\left(\mathrm{solution}\right)} \\ =\frac{\mathbf{0}\mathbf{.}\mathbf{547}\mathrm{mol}}{\mathbf{0}\mathbf{.}\mathbf{5}\mathrm{L}} \\ =\mathbf{1}\mathbf{.}\mathbf{10}\mathrm{mol}/\mathrm{L} \end{gathered}$$

Thus, the value of the formula concentration is $\mathbf{1}\mathbf{.}\mathbf{10}\mathrm{mol}/\mathrm{L}$.