# Determine the number of atoms in each sample. a.10.0 g Sr b.10.0 g Mg c.28.5 kg Zn

### Chemistry In Focus

7th Edition
Tro + 1 other
Publisher: Cengage Learning,
ISBN: 9781337399692

Chapter
Section

### Chemistry In Focus

7th Edition
Tro + 1 other
Publisher: Cengage Learning,
ISBN: 9781337399692
Chapter 3, Problem 49E
Textbook Problem
94 views

## Determine the number of atoms in each sample.a.10.0 g Srb.10.0 g Mgc.28.5 kg Zn

Interpretation Introduction

Interpretation:

The number of atoms in each sample is to be calculated.

Concept Introduction:

 A mole is a unit of amount of substance. It relates a number of particles to the molar mass.

 One mole of a substance contains Avogadro’s number, that is, 6.022×1023 particles. The number remains constant regardless of the nature of the substance. One mole of an atom contains 6.022×1023 atoms. One mole of molecules contains 6.022×1023 molecules.

 It also relates to the molar mass of a substance in grams. One mole of a substance weighs that amount in grams, which is equal to its molar mass.

### Explanation of Solution

a) 10.0 g Sr

The number of atoms in Sr is calculated as follows:

The molar mass of Sr is 87.62 g/mol.

6.022 ×1023 atoms of Sr = 1 mole of Sr = 87.62 g

87.62 g of Sr contains = 6.022 ×1023 atoms of Sr

Therefore,

10 g of Sr  contains =(10g Sr×1 mol Sr87.62 g Sr 6.022×1023 atoms1 mol Sr)                     =6.87 × 1022 atoms

Hence, the number of atoms in Sr is 6.87 × 1022 atoms .

b) 10.0 g Mg

The number of atoms in Mg is calculated as follows:

The molar mass of Mg is 24.31 g.

6.022 ×1023 atoms of Mg = 1 mole of Mg = 24.3 g

24.3 g of Mg contains = 6.022 ×1023 atoms of Mg

Thus,

10 g of Mg  contains=10g Mg×1 mol Mg24.31 g Mg× 6.022×1023 atoms1 mol Mg                     =  2

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