Chapter 7, Problem 1PE

(a)

Interpretation Introduction

Interpretation:

The molar mass of $\text{KBr}$ has to be given.

Answer to Problem 1PE

The molar mass of $\text{KBr}$ is $\text{119}\text{g}\text{.}$

Explanation of Solution

The molecular formula has one potassium atom, and one bromine atoms.  The molecular mass of $\text{KBr}$ can be calculated using the atomic masses of each atom in the molecular formula.

The atomic mass of potassium $\text{=39}\text{g}$

The atomic mass of bromine $\text{=80}\text{g}$

Adding the values of atomic masses of each atom the molar mass of $\text{KBr}$ is found as $\text{119}\text{g}\text{.}$

(b)

Interpretation Introduction

Interpretation:

The molar mass of ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}$ has to be given.

Answer to Problem 1PE

The molar mass of ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}$ is $\text{142}\text{g}\text{.}$

Explanation of Solution

Given,

The atomic mass of Sodium atom $\text{=23}\text{g}$

The atomic mass of sulfur atom $\text{=32}\text{g}$

The atomic mass of oxygen atom $\text{=16}\text{g}$

The molecular formula can be calculated as,

Molecular formula of ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}$$\text{=2×23+32+4×16}$

Molecular formula of ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}$$\text{=142}\text{g}$

The molar mass of ${\text{Na}}_{\text{2}}{\text{SO}}_{\text{4}}$ is $\text{142}\text{g}\text{.}$

(c)

Interpretation Introduction

Interpretation:

The molar mass of $\text{Pb}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}$ has to be given.

Answer to Problem 1PE

The molar mass of $\text{Pb}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}$ is $331.2\text{g}\text{.}$

Explanation of Solution

Given,

The atomic mass of lead atom $\text{=207}\text{.2}\text{g}$

The atomic mass of nitrogen atom $\text{=14}\text{g}$

The atomic mass of oxygen atom $\text{=16}\text{g}$

The molecular formula can be calculated as,

Molecular formula of $\text{Pb}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}$$\text{=207}\text{.2+2×(14+3×16)}$

Molecular formula of $\text{Pb}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}$$\text{=331}\text{.2}\text{g}$

The molar mass of $\text{Pb}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}$ is $331.2\text{g}\text{.}$

(d)

Interpretation Introduction

Interpretation:

The molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}$ has to be given.

Answer to Problem 1PE

The molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}$ is $46\text{g}\text{.}$

Explanation of Solution

Given,

The atomic mass of carbon atom $\text{=12}\text{g}$

The atomic mass of Hydrogen atom $\text{=1}\text{g}$

The atomic mass of oxygen atom $\text{=16}\text{g}$

The molecular formula can be calculated as,

Molecular formula of ${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}$$\text{=2}\times \text{12+6}\times \text{1+16}$

Molecular formula of ${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}$$\text{=46}\text{g}$

The molar mass of ${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}$ is $46\text{g}\text{.}$

(e)

Interpretation Introduction

Interpretation:

The molar mass of ${\text{HC}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}$ has to be given.

Answer to Problem 1PE

The molar mass of ${\text{HC}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}$ is $60\text{g}\text{.}$

Explanation of Solution

Given,

The atomic mass of carbon atom $\text{=12}\text{g}$

The atomic mass of Hydrogen atom $\text{=1}\text{g}$

The atomic mass of oxygen atom $\text{=16}\text{g}$

The molecular formula can be calculated as,

Molecular formula of ${\text{HC}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}$$\text{=2×12+4×1+2×16}$

Molecular formula of ${\text{HC}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}$$\text{=60}\text{g}$

The molar mass of ${\text{HC}}_{\text{2}}{\text{H}}_{\text{3}}{\text{O}}_{\text{2}}$ is $60\text{g}\text{.}$

(f)

Interpretation Introduction

Interpretation:

The molar mass of ${\text{Fe}}_{\text{3}}{\text{O}}_{\text{4}}$ has to be given.

Answer to Problem 1PE

The molar mass of ${\text{Fe}}_{\text{3}}{\text{O}}_{\text{4}}$ is $231.53\text{g}\text{.}$

Explanation of Solution

Given,

The atomic mass of iron atom $\text{=55}\text{.845}\text{g}$

The atomic mass of oxygen atom $\text{=16}\text{g}$

The molecular formula can be calculated as,

Molecular formula of ${\text{Fe}}_{\text{3}}{\text{O}}_{\text{4}}$$\text{=3×55}\text{.845+4×16}$

Molecular formula of ${\text{Fe}}_{\text{3}}{\text{O}}_{\text{4}}$$\text{=231}\text{.53}\text{g}$

The molar mass of ${\text{Fe}}_{\text{3}}{\text{O}}_{\text{4}}$ is $231.53\text{g}\text{.}$

(g)

Interpretation Introduction

Interpretation:

The molar mass of ${\text{C}}_{\text{12}}{\text{H}}_{\text{22}}{\text{O}}_{\text{11}}$ has to be given.

Answer to Problem 1PE

The molar mass of ${\text{C}}_{\text{12}}{\text{H}}_{\text{22}}{\text{O}}_{\text{11}}$ is $342\text{g}\text{.}$

Explanation of Solution

Given,

The atomic mass of carbon atom $\text{=12}\text{g}$

The atomic mass of hydrogen atom $\text{=1}\text{g}$

The atomic mass of oxygen atom $\text{=16}\text{g}$

The molecular formula can be calculated as,

Molecular formula of ${\text{C}}_{\text{12}}{\text{H}}_{\text{22}}{\text{O}}_{\text{11}}$$\text{=12×12+22}\times \text{1+11×16}$

Molecular formula of ${\text{C}}_{\text{12}}{\text{H}}_{\text{22}}{\text{O}}_{\text{11}}$$\text{=342}\text{g}$

The molar mass of ${\text{C}}_{\text{12}}{\text{H}}_{\text{22}}{\text{O}}_{\text{11}}$ is $342\text{g}\text{.}$

(h)

Interpretation Introduction

Interpretation:

The molar mass of ${\text{Al}}_{\text{2}}{\left({\text{SO}}_{\text{4}}\right)}_{\text{3}}$ has to be given.

Answer to Problem 1PE

The molar mass of ${\text{Al}}_{\text{2}}{\left({\text{SO}}_{\text{4}}\right)}_{\text{3}}$ is $342\text{g}\text{.}$

Explanation of Solution

Given,

The atomic mass of luminium atom $\text{=27}\text{g}$

The atomic mass of sulfur atom $\text{=32}\text{g}$

The atomic mass of oxygen atom $\text{=16}\text{g}$

The molecular formula can be calculated as,

Molecular formula of ${\text{Al}}_{\text{2}}{\left({\text{SO}}_{\text{4}}\right)}_{\text{3}}$$\text{=2×27+3}\times \text{(32+4×16)}$

Molecular formula of ${\text{Al}}_{\text{2}}{\left({\text{SO}}_{\text{4}}\right)}_{\text{3}}$$\text{=342}\text{g}$

The molar mass of ${\text{Al}}_{\text{2}}{\left({\text{SO}}_{\text{4}}\right)}_{\text{3}}$ is $342\text{g}\text{.}$

(i)

Interpretation Introduction

Interpretation:

The molar mass of ${\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{HPO}}_{\text{4}}$ has to be given.

Answer to Problem 1PE

The molar mass of ${\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{HPO}}_{\text{4}}$ is $132\text{g}\text{.}$

Explanation of Solution

Given,

The atomic mass of nitrogen atom $\text{=14}\text{g}$

The atomic mass of phosphorus atom $\text{=31}\text{g}$

The atomic mass of oxygen atom $\text{=16}\text{g}$

The atomic mass of hydrogen atom $\text{=1}\text{g}$

The molecular formula can be calculated as,

Molecular formula of ${\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{HPO}}_{\text{4}}$$\text{=2×}\left(\text{14+4×1}\right)\text{+1+31×1+4×16}$

Molecular formula of ${\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{HPO}}_{\text{4}}$$\text{=132}\text{g}$

The molar mass of ${\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{HPO}}_{\text{4}}$ is $132\text{g}\text{.}$