Chapter 10, Problem 48A

(a)

Interpretation Introduction

Interpretation: The 85.21cal of energy needs to be converted to joules.

Concept introduction: The following conversion factor can be used to solve the problem:

1cal=4.184J

Answer to Problem 48A

85.21cal=356.52J

Explanation of Solution

1cal=4.184J

Conversion of 85.21cal to J is as follows:

  $\begin{array}{c}\text{85}.\text{21}\cancel{\text{cal}}\text{×}\frac{\text{4}\text{.184J}}{1\cancel{\text{cal}}}=\text{85}.\text{21}\times \text{4}\text{.184J}\\ =356.52\text{J}\end{array}$

Thus 85.21cal=356.52J

(b)

Interpretation Introduction

Interpretation: The 672.1J energy needs to be converted to calories.

Concept introduction: The following conversion factor can be used to solve the problem:

1cal=4.184J

Answer to Problem 48A

672.1J=160.64 cal

Explanation of Solution

1cal=4.184J

Conversion of 672.1J to cal is as follows:

  $\begin{array}{c}\text{672}\text{.1}\cancel{\text{J}}\text{×}\frac{\text{1cal}}{\text{4}\text{.184}\cancel{\text{J}}}=\frac{672.1\text{cal}}{\text{4}\text{.184}}\\ =160.64\text{cal}\end{array}$

Thus 672.1J=160.64 cal

(c)

Interpretation Introduction

Interpretation: 8.921kJ of energy needs to be converted to joules.

Concept introduction: Kilo joule is SI unit of energy, which is equivalent to 1000 Joules.

Answer to Problem 48A

8.921kJ=8921J

Explanation of Solution

1kJ=1000J

Conversion of 8.921kJ to joules is as follows:

  $\begin{array}{c}\text{8}\text{.921}\cancel{\text{kJ}}\text{×}\frac{\text{1000J}}{\text{1}\cancel{\text{kJ}}}=\text{8}\text{.921}\times 1000\text{J}\\ =\text{8921J}\end{array}$

Thus 8.921kJ=8921J

(d)

Interpretation Introduction

Interpretation: 556.3 cal energy needs to be converted to kilojoules.

Concept introduction: The following conversion factors can be used to solve the given problem:

1kJ=1000J

1cal=4.184J

1kcal=1000cal

Answer to Problem 48A

556.3cal=2.33kJ

Explanation of Solution

1kJ=1000J

1cal=4.184J

1kcal=1000cal

Conversion of 556.3cal into kilojoules is as follows:

  $\begin{array}{c}\text{556}\text{.3}\cancel{\text{cal}}\text{×}\frac{\text{4}\text{.184}\cancel{\text{J}}}{\text{1}\cancel{\text{cal}}}\text{×}\frac{\text{1kJ}}{1000\cancel{\text{J}}}=\frac{\text{556}\text{.3}\times \text{4}\text{.184kJ}}{1000}\\ =2.33\text{kJ}\end{array}$

Thus 556.3cal=2.33kJ