Chapter 5, Problem 71E

Chloral hydrate (C₂H₃Cl₃O₂) is a drug formerly used as a sedative and hypnotic. It is the compound used to make “Mickey Finns” in detective stories.

a. Calculate the molar mass of chloral hydrate.

b. What amount (moles) of C₂H₃Cl₃O₂ molecules are in 500.0 g chloral hydrate?

c. What is the mass in grams of 2.0 × 10⁻² mole of chloral hydrate?

d. What number of chlorine atoms are in 5.0 g chloral hydrate?

e. What mass of chloral hydrate would contain 1.0 g CI?

f. What is the mass of exactly 500 molecules of chloral hydrate?

Interpretation Introduction

Interpretation: The answers are to be given for the given options.

Concept introduction: The atomic mass is defined as the sum of number of protons and number of neutrons.

Molar mass of a substance is defined as the mass of the substance in gram of one mole of that compound.

The molar mass of any compound can be calculated by adding of atomic weight of individual atoms present in it.

The amount of substance containing $\text{12}\text{g}$ of pure carbon is called a mole. One mole of atoms always contains $\text{6}\text{.022}\times {\text{10}}^{\text{23}}$ molecules. The number of molecules in one mole is also called Avogadro’s number.

To determine: The molar mass of chloral hydrate $\left({\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\right)$.

Explanation of Solution

The atomic weight of carbon $\left(\text{C}\right)$ is $\text{12}\text{.01}\text{g}/\text{mol}$.

The atomic weight of oxygen $\left(\text{O}\right)$ is $\text{16}\text{.00}\text{g}/\text{mol}$.

The atomic weight of hydrogen $\left(\text{H}\right)$ is $\text{1}\text{.008}\text{g}/\text{mol}$.

The atomic weight of chlorine $\left(\text{Cl}\right)$ is $\text{35}\text{.453}\text{g}/\text{mol}$.

In compound ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$, two carbon, two oxygen, three chlorine and three hydrogen atoms are present. Hence, molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is calculated as,

$\left[\begin{array}{l}\text{3}\left(\text{1}\text{.008}\text{g}/\text{mol}\right)+\text{2}\left(\text{12}\text{.01}\text{g}/\text{mol}\right)\\ +\text{2}\left(\text{16}\text{.00}\text{g}/\text{mol}\right)+\text{3}\left(\text{35}\text{.453}\text{g/mol}\right)\end{array}\right]=\underset{\_}{165.403g/mol}$

The molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\underset{\_}{165.403g/mol}$.

Conclusion

Molar mass is defined as mass of $\text{6}\text{.022}\times {\text{10}}^{\text{23}}$ atoms or molecules of that substance.

Interpretation Introduction

Interpretation: The answers are to be given for the given options.

Concept introduction: The atomic mass is defined as the sum of number of protons and number of neutrons.

Molar mass of a substance is defined as the mass of the substance in gram of one mole of that compound.

The molar mass of any compound can be calculated by adding of atomic weight of individual atoms present in it.

The amount of substance containing $\text{12}\text{g}$ of pure carbon is called a mole. One mole of atoms always contains $\text{6}\text{.022}\times {\text{10}}^{\text{23}}$ molecules. The number of molecules in one mole is also called Avogadro’s number.

To determine: The number of moles in $\text{500}\text{.00}\text{g}$ of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$.

Explanation of Solution

Given

The mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\text{500}\text{.00}\text{g}$.

The molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\text{165}\text{.403}\text{g/mol}$

Formula

The number of moles in ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is calculated as,

$\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\frac{\text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}{\text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}$

Substitute the values of mass and molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ in above equation,

$\begin{array}{c}\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\frac{\text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}{\text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}\\ =\frac{\text{500}\text{g}}{\text{165}\text{.403}\text{g/mol}}\\ =\underset{\_}{3.0229mol}\end{array}$

The number of moles in $\text{500}\text{.00}\text{g}$ of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\underset{\_}{3.0229mol}$.

Conclusion

Number of moles is calculated by dividing the given mass with the molar mass of that compound.

Interpretation Introduction

Interpretation: The answers are to be given for the given options.

Concept introduction: The atomic mass is defined as the sum of number of protons and number of neutrons.

Molar mass of a substance is defined as the mass of the substance in gram of one mole of that compound.

The molar mass of any compound can be calculated by adding of atomic weight of individual atoms present in it.

The amount of substance containing $\text{12}\text{g}$ of pure carbon is called a mole. One mole of atoms always contains $\text{6}\text{.022}\times {\text{10}}^{\text{23}}$ molecules. The number of molecules in one mole is also called Avogadro’s number.

To determine: The mass of $\text{2}\text{.0}\times {\text{10}}^{-\text{2}}\text{mol}$ ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$.

Explanation of Solution

Given

The moles of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\text{2}\text{.0}\times {\text{10}}^{-\text{2}}\text{mol}$.

The molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\text{165}\text{.403}\text{g/mol}$

Formula

The mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is calculated as,

$\begin{array}{l}\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\frac{\text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}{\text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}\\ \text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\times \text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\end{array}$

Substitute the values of moles and molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ in above equation.

$\begin{array}{c}\text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\times \text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\\ =\text{165}\text{.403}\text{g/mol}\times \text{2}\text{.0}\times {\text{10}}^{-\text{2}}\text{mol}\\ =\underset{\_}{3.30806g}\end{array}$

The mass of $\text{2}\text{.0}\times {\text{10}}^{-\text{2}}\text{mol}$ ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\underset{\_}{3.30806g}$.

Conclusion

Mass of molecule is calculated by multiplying the number of moles and molar mass of that molecule.

Interpretation Introduction

Interpretation: The answers are to be given for the given options.

Concept introduction: The atomic mass is defined as the sum of number of protons and number of neutrons.

Molar mass of a substance is defined as the mass of the substance in gram of one mole of that compound.

The molar mass of any compound can be calculated by adding of atomic weight of individual atoms present in it.

The amount of substance containing $\text{12}\text{g}$ of pure carbon is called a mole. One mole of atoms always contains $\text{6}\text{.022}\times {\text{10}}^{\text{23}}$ molecules. The number of molecules in one mole is also called Avogadro’s number.

To determine: The number of chlorine $\left(\text{Cl}\right)$ atoms in $\text{5}\text{.00}\text{g}$ of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$.

Explanation of Solution

Given

The mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\text{5}\text{.00}\text{g}$.

The molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\text{165}\text{.403}\text{g/mol}$.

Formula

The number of moles of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is calculated as,

$\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\frac{\text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}{\text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}$

Substitute the values of mass and molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ in above equation,

$\begin{array}{c}\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\frac{\text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}{\text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}\\ =\frac{\text{5}\text{.00}\text{g}}{\text{165}\text{.403}\text{g/mol}}\\ =\text{0}\text{.03022}\text{mol}\end{array}$

Since, one mole of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is equal to three moles of chlorine, Therefore, $\text{0}\text{.03022}\text{mol}$ of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is equal to

$\text{3}\times \text{0}\text{.03022}\text{mol}=\text{0}\text{.09066}\text{mol}$ of chlorine $\left(\text{Cl}\right)$.

The number of chlorine atoms in ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is calculated using the formula,

$\text{Number}\text{of}\text{Cl}\text{atoms}=\text{Moles}\text{of}\text{Cl}\times \text{6}\text{.022}\times {\text{10}}^{\text{23}}$

Substitute the value of number of moles of $\text{Cl}$ atom in above equation,

$\begin{array}{c}\text{Number}\text{of}\text{Cl}\text{atoms}=\text{Moles}\text{of}\text{Cl}\times \text{6}\text{.022}\times {\text{10}}^{\text{23}}\\ =\text{0}\text{.09066}\text{mol}\times \text{6}\text{.022}\times {\text{10}}^{\text{23}}\\ =\underset{\_}{5.46\times 10^{22}atoms}\end{array}$

The number of chlorine $\left(\text{Cl}\right)$ atoms in $\text{5}\text{.00}\text{g}$ of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\underset{\_}{5.46\times 10^{22}atoms}$.

Conclusion

The number of atoms is calculated by multiplying the number of moles with Avogadro’s number.

Interpretation Introduction

Interpretation: The answers are to be given for the given options.

Concept introduction: The atomic mass is defined as the sum of number of protons and number of neutrons.

Molar mass of a substance is defined as the mass of the substance in gram of one mole of that compound.

The molar mass of any compound can be calculated by adding of atomic weight of individual atoms present in it.

The amount of substance containing $\text{12}\text{g}$ of pure carbon is called a mole. One mole of atoms always contains $\text{6}\text{.022}\times {\text{10}}^{\text{23}}$ molecules. The number of molecules in one mole is also called Avogadro’s number.

To determine: The mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$. in $\text{1}\text{.00}\text{g}$ of $\text{Cl}$.

Explanation of Solution

Given

The mass of $\text{Cl}$ is $\text{1}\text{.00}\text{g}$.

The atomic mass of $\text{Cl}$ is $\text{35}\text{.453}\text{g/mol}$

The molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\text{165}\text{.403}\text{g/mol}$.

Formula

The moles of $\text{Cl}$ is calculated as,

$\text{Moles}\text{of}\text{Cl}=\frac{\text{Mass}\text{of}\text{Cl}}{\text{Atomic}\text{mass}\text{of}\text{Cl}}$

Substitute the values of mass and atomic mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ in above equation.

$\begin{array}{c}\text{Moles}\text{of}\text{Cl}=\frac{\text{Mass}\text{of}\text{Cl}}{\text{Atomic}\text{mass}\text{of}\text{Cl}}\\ =\frac{\text{1}\text{.00}\text{g}}{\text{35}\text{.454}}\\ =\text{0}\text{.0282}\text{mol}\end{array}$

Since, one mole of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is equal to three moles of chlorine, Therefore, $\text{0}\text{.0282}\text{mol}$ of $\text{Cl}$ is equal to

$\frac{\text{0}\text{.0282}\text{mol}}{\text{3}}=\text{0}\text{.0094}\text{mol}$ of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$.

The mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is calculated as,

$\begin{array}{l}\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\frac{\text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}{\text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}\\ \text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\times \text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\end{array}$

Substitute the values of moles and molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ in above equation.

$\begin{array}{c}\text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\times \text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\\ =\text{165}\text{.403}\text{g/mol}\times \text{0}\text{.0094}\text{mol}\\ =\underset{\_}{1.555g}\end{array}$

The mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$. in $\text{1}\text{.00}\text{g}$ of $\text{Cl}$ is $\underset{\_}{1.555g}$.

Conclusion

Mass of molecule is calculated by multiplying the number of moles and molar mass of that molecule.

Interpretation Introduction

Interpretation: The answers are to be given for the given options.

Concept introduction: The atomic mass is defined as the sum of number of protons and number of neutrons.

Molar mass of a substance is defined as the mass of the substance in gram of one mole of that compound.

The molar mass of any compound can be calculated by adding of atomic weight of individual atoms present in it.

The amount of substance containing $\text{12}\text{g}$ of pure carbon is called a mole. One mole of atoms always contains $\text{6}\text{.022}\times {\text{10}}^{\text{23}}$ molecules. The number of molecules in one mole is also called Avogadro’s number.

To determine: The mass of exactly $\text{500}\text{molecules}$ of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$.

Explanation of Solution

Given

The total molecules in ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\text{500}\text{molecules}$.

The molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\text{165}\text{.403}\text{g/mol}$.

Since one mole of atoms always contains $\text{6}\text{.022}\times {\text{10}}^{\text{23}}$ molecules. Therefore, number of moles in $\text{500}\text{molecules}$ is,

$\frac{\text{500}}{\text{6}\text{.022}\times {\text{10}}^{\text{23}}}\text{mol}=\text{83}\text{.028}\times {\text{10}}^{-\text{23}}\text{mol}$

Formula

The mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is calculated as,

$\begin{array}{l}\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\frac{\text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}{\text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}}\\ \text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\times \text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\end{array}$

Substitute the values of moles and molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ in above equation.

$\begin{array}{c}\text{Mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}=\text{Moles}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\times \text{Molar}\text{mass}\text{of}{\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}\\ =\text{165}\text{.403}\text{g/mol}\times \text{83}\text{.028}\times {\text{10}}^{-\text{23}}\text{mol}\\ =\underset{\_}{1.373\times 10^{-19}g}\end{array}$

The mass of exactly $\text{500}\text{molecules}$ of ${\text{C}}_{\text{2}}{\text{H}}_{\text{3}}{\text{Cl}}_{\text{3}}{\text{O}}_{\text{2}}$ is $\underset{\_}{1.373\times 10^{-19}g}$.

Conclusion

Mass of molecule is calculated by multiplying the number of moles and molar mass of that molecule.