Chapter 10, Problem 191A

Interpretation Introduction

Interpretation:

The unknown element must be found out for which mass of one atom is $\text{6}{\text{.66×10}}^{\text{-23}}\text{g}\text{.}$

Concept introduction:

One mole of any element contains Avogadro’s number ( $\text{6}{\text{.023×10}}^{\text{23}}$ ) of atoms.

Answer to Problem 191A

The unknown element is calcium (Ca).

Explanation of Solution

Mass of 1 atom is $\text{6}{\text{.66×10}}^{\text{-23}}\text{g}\text{.}$

Thus mass of $\text{6}{\text{.023×10}}^{\text{23}}$ atoms $\text{=6}{\text{.66×10}}^{\text{-23}}\times \text{6}{\text{.023×10}}^{\text{23}}\text{ g=40}\text{.11 g}\text{.}$

This is mass of 1 mol of Ca atom or molar mass of Ca atom thus, the unknown element is calcium.

Conclusion

Atomic mass of the unknown element is 40.11 g which is calcium (Ca).