91影视

Molarity is defined as the number of moles of solute per liter solution.

$$\begin{gathered} \mathbf{\text{molarity}}\mathbf{=}\frac{\mathbf{\text{尘辞濒别蝉鈥塷蹿鈥塻辞濒耻迟别}}}{\mathbf{\text{惫辞濒耻尘别鈥嬧赌夆赌媜蹿鈥塻辞濒耻迟颈辞苍鈥�}}\mathbf{\left(}\mathbf{L}\mathbf{\right)}} \\ \mathbf{\text{尘辞濒别蝉鈥夆赌媜蹿鈥嬧赌塻辞濒耻迟别}}\mathbf{=}\frac{\mathbf{\text{尘补蝉蝉鈥塷蹿鈥塻辞濒耻迟别}}}{\mathbf{\text{molar鈥壋静共醪踱�塷蹿鈥塻辞濒耻迟别}}} \end{gathered}$$

Given that,$4.50脳{10}^{鈭�5}M$ is the fluoride molarity or concentration to be obtained and volume of blending tank of water is $5000\text{L}$.

Molar mass of$\text{NaF}$is defined as below.

Molarity is defined as the number of moles of solute per liter solution.

One mole of fluoride is given by one mole of $\text{NaF}$.

Thus, Fluoride concentration is equivalent to the concentration of $\text{NaF}$.

Hence, the mass of$\text{NaF}$can be calculated as,

role="math" localid="1663331625931" $$\begin{gathered} \text{molarity}=\frac{\text{尘补蝉蝉鈥嬧赌塷蹿鈥塏补贵}}{\text{尘辞濒补谤鈥夆赌媘补蝉蝉鈥塷蹿鈥塏补贵}}脳\frac{\text{1}}{\text{volume}\left(L\right)} \\ 4.50脳{10}^{鈭�5}M=\frac{\text{尘补蝉蝉鈥嬧赌塷蹿鈥塏补贵}}{\text{41.99}{\displaystyle \raisebox{1ex}{$\text{鈥塯}$}\!\left/ \!\raisebox{-1ex}{$\text{mol}$}\right.}}脳\frac{\text{1}}{\text{5000L}} \\ \frac{\text{尘补蝉蝉鈥嬧赌塷蹿鈥塏补贵}}{\text{41.99}{\displaystyle \raisebox{1ex}{$\text{鈥塯}$}\!\left/ \!\raisebox{-1ex}{$\text{mol}$}\right.}}=4.50脳{10}^{鈭�5}M脳\text{5000L} \\ \text{尘补蝉蝉鈥塷蹿鈥塏补贵}=\text{9.45g} \end{gathered}$$

Therefore,$9.45\text{g}$ of$\text{NaF}$ needs to attain a fluoride concentration of $4.50脳{10}^{鈭�5}M$.

Molar mass of fluoride is$\text{18.99}\raisebox{1ex}{${\displaystyle \text{g}}$}\!\left/ \!\raisebox{-1ex}{$\text{mol}$}\right.$ and volume is $\text{2.0L}$.

Fluoride concentration is equal to$\text{NaF}$ concentration.

Thus, the mass of fluoride can be calculated as follow.

$$\begin{gathered} \text{molarity}=\frac{\text{尘补蝉蝉鈥嬧赌塷蹿鈥塅}}{\text{尘辞濒补谤鈥夆赌媘补蝉蝉鈥塷蹿鈥塅}}脳\frac{\text{1}}{\text{volume}\left(L\right)} \\ 4.50脳{10}^{鈭�5}M=\frac{\text{尘补蝉蝉鈥嬧赌塷蹿鈥塅}}{\text{18.99鈥�}{\displaystyle \raisebox{1ex}{$\text{g}$}\!\left/ \!\raisebox{-1ex}{$\text{mol}$}\right.}}脳\frac{\text{1}}{\text{2.0L}} \\ \frac{{\displaystyle \text{尘补蝉蝉鈥嬧赌塷蹿鈥塅}}}{{\displaystyle \text{18.99鈥�}\raisebox{1ex}{$\text{g}$}\!\left/ \!\raisebox{-1ex}{$\text{mol}$}\right.}}=4.50脳{10}^{鈭�5}M脳2.0\text{L} \\ \text{尘补蝉蝉鈥塷蹿鈥塅}=1.70\text{g} \end{gathered}$$

Hence, the mass of fluoride is$1.70\text{g}$ per day ingested by a person who drink$2.0\text{L}$ of this water.