Chapter 2, Problem 2.80P

Interpretation Introduction

(a)

Interpretation:

The percentage of mass contributed by neutrons in Carbon-12 is to be calculated.

Concept Introduction:

Atomic mass is the sum of the number of the proton and number of the neutron present in the nucleus of an atom.

Answer to Problem 2.80P

Neutrons contribute 50% of mass in carbon-12.

Explanation of Solution

The atomic number of carbon is 6, and the atomic mass is 12.

The atomic number (Z) = equal to the number of protons.

Therefore, number of protons in the Carbon-12 nucleus is 6.

The atomic mass is given as.

$\begin{array}{c}\text{a}=\text{number}\text{of}\text{proton}+\text{number}\text{of}\text{neutron}\\ \text{12}=\text{6}+n\\ n=6\end{array}$

Therefore, contribution of neutrons in the mass of carbon-12 is calculated as.

$m\text{a}ss\%=\frac{\text{number}\text{of}\text{neutron}}{\text{Atomic}\text{mass}}\times 100$

Putting the values in the above equation.

$\begin{array}{c}m\text{a}ss\%=\frac{6}{12}\times 100\\ =50\%\end{array}$

Interpretation Introduction

(b)

Interpretation:

Percentage of mass contributed by neutrons in Calcium-40 is to be calculated.

Concept Introduction:

Atomic mass is the sum of the number of the proton and number of the neutron present in the nucleus of an atom.

Answer to Problem 2.80P

Neutrons contribute 50% of mass in calcium-40.

Explanation of Solution

The atomic number of Calcium is 20, and the atomic mass is 40.

The atomic number (Z) = equal to the number of protons.

Therefore, number of protons in the Calcium-40 nucleus is 20.

The atomic mass is given as.

$\begin{array}{c}\text{a}=\text{number}\text{of}\text{proton}+\text{number}\text{of}\text{neutron}\\ \text{40}=\text{20}+n\\ n=20\end{array}$

Therefore, contribution of neutrons in the mass of Calcium-40 is calculated as.

$m\text{a}ss\%=\frac{\text{number}\text{of}\text{neutron}}{\text{Atomic}\text{mass}}\times 100$

Putting the values in the above equation.

$\begin{array}{c}m\text{a}ss\%=\frac{20}{40}\times 100\\ =50\%\end{array}$

Interpretation Introduction

(c)

Interpretation:

Percentage of mass contributed by neutrons in Iron-55 is to be calculated.

Concept Introduction:

Atomic mass is the sum of the number of the proton and number of the neutron present in the nucleus of an atom.

Answer to Problem 2.80P

Neutrons contribute 52.72% of mass in Iron-55.

Explanation of Solution

The atomic number of Iron is 26, and the atomic mass is 55.

The atomic number (Z) = equal to the number of protons.

Therefore, number of protons in the Iron-55 nucleus is 26.

The atomic mass is given as.

$\begin{array}{c}\text{a}=\text{number}\text{of}\text{proton}+\text{number}\text{of}\text{neutron}\\ \text{55}=2\text{6}+n\\ n=29\end{array}$

Therefore, contribution of neutrons in the mass of Iron-55is calculated as.

$m\text{a}ss\%=\frac{\text{number}\text{of}\text{neutron}}{\text{Atomic}\text{mass}}\times 100$

Putting the values in the above equation.

$\begin{array}{c}m\text{a}ss\%=\frac{29}{55}\times 100\\ =52.72\%\end{array}$

Interpretation Introduction

(d)

Interpretation:

Percentage of mass contributed by neutrons in Bromine-79 is to be calculated.

Concept Introduction:

Atomic mass is the sum of the number of the proton and number of the neutron present in the nucleus of an atom.

Answer to Problem 2.80P

Neutrons contribute 55.69% of mass in Bromine-79.

Explanation of Solution

The atomic number of Bromine-79 is 35, and the atomic mass is 79.

The atomic number (Z) = equal to the number of protons.

Therefore, number of protons in the Bromine-79 nucleus is 35.

The atomic mass is given as.

$\begin{array}{c}\text{a}=\text{number}\text{of}\text{proton}+\text{number}\text{of}\text{neutron}\\ \text{79}=35+n\\ n=44\end{array}$

Therefore, contribution of neutrons in the mass of Bromine-79 is calculated as.

$m\text{a}ss\%=\frac{\text{number}\text{of}\text{neutron}}{\text{Atomic}\text{mass}}\times 100$

Putting the values in the above equation.

$\begin{array}{c}m\text{a}ss\%=\frac{44}{79}\times 100\\ =55.69\%\end{array}$

Interpretation Introduction

(e)

Interpretation:

Percentage of mass contributed by neutrons in Platinum-195 is to be calculated.

Concept Introduction:

Atomic mass is the sum of the number of the proton and number of the neutron present in the nucleus of an atom.

Answer to Problem 2.80P

Neutrons contribute 60% of mass in Platinum-195.

Explanation of Solution

The atomic number of Platinum-195 is 78, and the atomic mass is 195.

The atomic number (Z) = equal to the number of protons.

Therefore, number of protons in the Platinum-195 nucleus is 78.

The atomic mass is given as.

$\begin{array}{c}\text{a}=\text{number}\text{of}\text{proton}+\text{number}\text{of}\text{neutron}\\ \text{195}=78+n\\ n=117\end{array}$

Therefore, contribution of neutrons in the mass of Platinum is calculated as.

$m\text{a}ss\%=\frac{\text{number}\text{of}\text{neutron}}{\text{Atomic}\text{mass}}\times 100$

Putting the values in the above equation.

$\begin{array}{c}m\text{a}ss\%=\frac{117}{195}\times 100\\ =60\%\end{array}$

Interpretation Introduction

(f)

Interpretation:

Percentage of mass contributed by neutrons in Uranium-238 is to be calculated.

Concept Introduction:

Atomic mass is the sum of the number of the proton and number of the neutron present in the nucleus of an atom.

Answer to Problem 2.80P

Neutrons contribute 61.34% of mass in Uranium-238.

Explanation of Solution

The atomic number of Uranium-238 is 92, and the atomic mass is 238.

The atomic number (Z) = equal to the number of protons.

Therefore, number of protons in the Uranium-238 nucleus is 92.

The atomic mass is given as.

$\begin{array}{c}\text{a}=\text{number}\text{of}\text{proton}+\text{number}\text{of}\text{neutron}\\ \text{238}=92+n\\ n=146\end{array}$

Therefore, contribution of neutrons in the mass of Uranium-238 is calculated as.

$m\text{a}ss\%=\frac{\text{number}\text{of}\text{neutron}}{\text{Atomic}\text{mass}}\times 100$

Putting the values in the above equation.

$\begin{array}{c}m\text{a}ss\%=\frac{146}{238}\times 100\\ =61.34\%\end{array}$