Chapter 6, Problem 3A

Interpretation Introduction

Interpretation : The term amu has to be defined and its value in grams has to be stated.

Concept Introduction : The mass of atom being small in size is difficult to be determined. Thus, relative masses of atoms have been calculated and carbon-12 has been chosen as the reference for determining the atomic mass of all the other atoms.

Answer to Problem 3A

One amu is equal to the mass of $\frac{1}{{12}^{\text{th}}}$ one atom of carbon-12. It is written as atomic mass unit.

One amu is equivalent to $1.66\times {10}^{-24}\text{grams}$ .

Explanation of Solution

One amu is equal to the mass of $\frac{1}{{12}^{\text{th}}}$ one atom of carbon-12. It is written as atomic mass unit. This unit is used for defining the mass of atoms as they are small in size. It basically determines the mass of one atom of an element.

The mass of one atom of carbon-12 is $1.99\times {10}^{-23}\text{grams}$ . The conversion of amu to grams is done using the definition of amu and is shown below.

  $\begin{array}{c}1amu=\frac{1}{12}\times \text{Mass of an atom of carbon}-12\\ =\frac{1}{12}\times 1.99\times {10}^{-23}\text{g}\\ \text{=1}\text{.66}\times {10}^{-24}\text{g}\end{array}$

Conclusion

One amu is equal to the mass of $\frac{1}{{12}^{\text{th}}}$ one atom of carbon-12. It is written as atomic mass unit.

One amu is equivalent to $1.66\times {10}^{-24}\text{grams}$ .