An anhydrous (water remove) salt has a formula mass of 186.181 g/mol. If the hydrated version of the salt has 8 mol of water associated with it, what is the mass % of water in the hydrated salt?

Respuesta :

Answer: The mass percent of water in the hydrated salt is 43.6 %

Explanation:

To calculate the mass for given number of moles, we use the equation:

[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex]

Moles of water = 8 moles

Molar mass of water = 18 g/mol

Putting values in above equation, we get:

[tex]8moles=\frac{\text{Mass of water}}{18g/mol}\\\\\text{Mass of water}=(8mol\times 18g/mol)=144g[/tex]

We are given:

Mass of anhydrous salt = 186.181 g

To calculate the mass percentage of water in the hydrated salt, we use the equation:

[tex]\text{Mass percent of water}=\frac{\text{Mass of water}}{\text{Mass of hydrated salt}}\times 100[/tex]

Mass of hydrated salt = [186.181 + 144]g = 330.181g

Mass of water = 144 g

Putting values in above equation, we get:

[tex]\text{Mass percent of water}=\frac{144g}{330.181g}\times 100=43.6\%[/tex]

Hence, the mass percent of water in the hydrated salt is 43.6 %

The mass percent of water in the hydrated salt is 43.6 %

Firstly, find the mass of water using given number of moles.

[tex]\text{ Number of moles}=\frac{\Given Mass}{\text{Molar mass}}[/tex]

Moles of water = 8 moles

Molar mass of water = 18 g/mol

On substituting the values:

[tex]\text{Mass}= \text{Molar mass} * \text{ Number of moles}= 18 \text{g/mol} * 8 \text{moles} =144 \text{g}[/tex]

Given:

Mass of anhydrous salt = 186.181 g

In order to calculate the mass percentage of water in the hydrated salt, the formula to be used is:

[tex]\text{ Mass percent of water}= \frac{\text{Mass of water}}{\text{Mass of hydrated salt}} * 100[/tex]

Since, Hydrated salt= (water+ salt)

Therefore mass of hydrated salt= [186.181 g + 144 g]= 330.181 g

 Substituting the  values in above equation, we get:

[tex]\text{ Mass percent of water}= \frac{144}{330.181} * 100=43.6\%[/tex]

Hence, the mass percent of water in the hydrated salt is 43.6 %

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