Chapter 2.7, Problem 2.5WE

(a)

Interpretation Introduction

Interpretation:

The number of carbon atom should be calculated in a sample containing 0.515 g of carbon.

Concept introduction:

$\begin{array}{l}\text{Avogadro’s number is 6}{\text{.022 × 10}}^{\text{23}}\\ \text{1 mole = }\text{6}{\text{.022 × 10}}^{\text{23}}\text{Avogadro’s number }\end{array}$

$\text{mol × }\frac{\text{6}{\text{.022 × 10}}^{\text{23}}\text{ atoms}}{\text{1 mol }}\text{=}\text{ atoms}$

(b)

Interpretation Introduction

Interpretation:

The mass of helium should be calculated in a sample containing $\text{6}{\text{.89×10}}^{\text{18}}\text{helium}\text{atoms}$ of carbon.

Concept introduction:

$\begin{array}{l}\text{Avogadro’s number is 6}{\text{.022 × 10}}^{\text{23}}\\ \text{1 mole = }\text{6}{\text{.022 × 10}}^{\text{23}}\text{Avogadro’s number }\end{array}$

$\text{mol × }\frac{\text{6}{\text{.022 × 10}}^{\text{23}}\text{ atoms}}{\text{1 mol }}\text{=}\text{ atoms}$