Chapter 10, Problem 74A

(a)

Interpretation Introduction

Interpretation: To determine the mass of the compound.

Concept Introduction: Mass percentage can be determined by the ratio of mass of the element and the mass of the compound which can be written as:

  $\text{Mass}\text{\%=}\frac{\text{Mass}\text{of}\text{}\text{element}}{\text{Mass}\text{of}\text{}\text{compound}}\text{×100}$

Answer to Problem 74A

The mass of sulphur atom will be 3.33 gram.

Explanation of Solution

The given compound is ${\text{H}}_{\text{2}}\text{S}$ .

Mass of hydrogen atom = 2 g/mol

Mass of sulphur atom = 32 g/mol

Mass of ${\text{H}}_{\text{2}}\text{S}$ = 34 g/mol

The mass of percentage can be determined by using the formula:

  $\text{Mass}\text{\%=}\frac{\text{Mass}\text{of}\text{}\text{element}}{\text{Mass}\text{of}\text{}\text{compound}}\text{×100}$

Put the given data in the above equation.

  $\begin{array}{c}\text{\%}\text{H}\text{=}\frac{2}{\text{34}}\text{×100}\\ \text{=5}\text{.88}\%\end{array}$

  $\begin{array}{c}\text{\%}\text{S}\text{=}\frac{32}{\text{34}}\text{×100}\\ \text{=94}\text{.12}\%\end{array}$

The number of grams of sulphur atom can be determined as:

  $\begin{array}{c}\text{Mass}\text{of}\text{S=}\text{0}\text{.94×3}\text{.54}\text{g}\\ \text{=}\text{3}\text{.33}\text{g}\end{array}$

Therefore, the mass of sulphur atom will be 3.33 gram.

(b)

Interpretation Introduction

Interpretation: To determine the mass of the compound.

Concept Introduction: Mass percentage can be determined by the ratio of the mass of the element and the mass of the compound which can be written as:

  $\text{Mass}\text{\%=}\frac{\text{Mass}\text{of}\text{}\text{element}}{\text{Mass}\text{of}\text{}\text{compound}}\text{×100}$

Answer to Problem 74A

The mass of nitrogen atom will be 5.6 gram.

Explanation of Solution

The given compound is ${\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{C}}_{\text{2}}{\text{O}}_{\text{4}}$ .

The molecular mass of ${\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{C}}_{\text{2}}{\text{O}}_{\text{4}}$ is $124.1 \text{g/mol}$

The molar mass of hydrogen atom = 1 g/mol

The molar mass of oxygen atom = 16 g/mol

The molar mass of nitrogen atom = 14 g/mol

The molar mass of carbon atom = 12 g/mol

Mass of the percentage can be determined by using the formula:

  $\text{Mass}\text{\%=}\frac{\text{Mass}\text{of}\text{}\text{element}}{\text{Mass}\text{of}\text{}\text{compound}}\text{×100}$

Put the given data in the above equation.

  $\begin{array}{c}\text{\%}\text{N}\text{=}\frac{2\times 14}{124.1 \text{g/mol}}\text{×100}\\ \text{=22}\text{.5}\%\end{array}$

Therefore, the number of grams of nitrogen atom can be determined as:

  $\begin{array}{c}\text{Mass}\text{of}\text{N=}0.\text{225}\text{×25}\text{g}\\ \text{=}5.6\text{g}\end{array}$

Therefore, the mass of nitrogen atom will be 5.6 gram.

(c)

Interpretation Introduction

Interpretation: To determine the mass of the compound.

Concept Introduction: Mass percentage can be determined by the ration of mass of element and mass of the compound which can be written as:

  $\text{Mass}\text{\%=}\frac{\text{Mass}\text{of}\text{}\text{element}}{\text{Mass}\text{of}\text{}\text{compound}}\text{×100}$

Answer to Problem 74A

The mass of Mg atom will be 39.93 gram.

Explanation of Solution

The given compound is ${\text{Mg(OH)}}_{\text{2}}$ .

Mass of $\text{Mg}$ atom = 24 g/mol

Mass of oxygen atom =32 g/mol

Mass of hydrogen atom = 2 g/mol

Mass of ${\text{Mg(OH)}}_{\text{2}}$ = 58.31 g/mol

Mass of percentage can be determined by using the formula:

Put the given data in the above equation.

  $\begin{array}{c}\text{\%}\text{H}\text{=}\frac{2.016}{58.31}\text{×100}\\ \text{=}3.45\%\end{array}$

  $\begin{array}{c}\text{\%}\text{Mg}\text{=}\frac{24.30}{58.31}\text{×100}\\ \text{=41}\text{.67}\%\end{array}$

  $\begin{array}{c}\text{\%}\text{O}\text{=}\frac{32}{58.31}\text{×100}\\ \text{=54}\text{.87}\%\end{array}$

Therefore, the number of grams of Mg atom can be determined as:

  $\begin{array}{c}\text{Mass}\text{of}\text{Mg=}0.41\text{×97}\text{.4}\text{g}\\ \text{=}39.93\text{g}\end{array}$

Therefore, the mass of Mg atom will be 39.93 gram.

(d)

Interpretation Introduction

Interpretation: To determine the mass of the compound.

Concept Introduction: Mass percentage can be determined by the ration of mass of element and mass of the compound which can be written as:

Answer to Problem 74A

The mass of P will be 14.4 g.

Explanation of Solution

The given compound is ${\text{Na}}_{\text{3}}{\text{(PO}}_{\text{4}}\text{)}$ .

Mass of Na atom = 69 g/mol

Mass of oxygen atom =64 g/mol

Mass of P atom = 31 g/mol

Mass of ${\text{Na}}_{\text{3}}{\text{(PO}}_{\text{4}}\text{)}$ = 164 g/mol

Mass of percentage can be determined by using the formula:

  $\text{Mass}\text{\%=}\frac{\text{Mass}\text{of}\text{}\text{element}}{\text{Mass}\text{of}\text{}\text{compound}}\text{×100}$

Put the given data in the above equation.

  $\begin{array}{c}\text{\%}\text{Na}\text{=}\frac{69}{164}\text{×100}\\ \text{=}42.1\%\end{array}$

  $\begin{array}{c}\text{\%}\text{P}\text{=}\frac{31}{164}\text{×100}\\ \text{=18}\%\end{array}$

  $\begin{array}{c}\text{\%}\text{O}\text{=}\frac{64}{164}\text{×100}\\ \text{=39}\%\end{array}$

Therefore, the number of grams of P atom can be determined as:

  $\begin{array}{c}\text{Mass}\text{of}\text{P=}0.18\text{×}80.4\text{g}\\ \text{=}14.4\text{g}\end{array}$

The mass of P will be 14.4 g.