Q. 3.28 - An Introduction to General, Organic, and Biological Chemistry

Question

A person uses$750 kcal$ on a long walk. Calculate the energy used for the walk in each of the following energy units:

$\left(a\right)$ joules

$\left(b\right)$ kilojoules

Step-by-Step Solution

Answer

Part $\left(a\right)$

$\left(a\right)$The converting energy in joules at $750 \mathrm{kcal}=3.14\times {10}^6\mathrm{J}.$

Part $\left(b\right)$

$\left(b\right)$The converting energy into kilojoules at $750 kcal=3.14\times {10}^3\mathrm{kJ}.$

Step: 1 Given information: (Part a)

A person uses for a long walk given are:$750kcal.$

To calculate the amount of energy expended on a walk is converting into joules.

Step: 2 Converting into joules: (Part a)

Use the appropriate conversion factor to convert energy into joules.

$1\mathrm{kcal}=1000\mathrm{cal}$

$1\mathrm{kcal}=4184\text{ joule }$

The factor will be as,

$\left(\frac{4184\text{ joule }}{1\text{ kcal }}\right)$

Changing  into joules will be as,

$750\mathrm{kcal}\times \frac{4184\mathrm{J}}{1\mathrm{kcal}}=3.14\times {10}^6\mathrm{J}$

As a result,$750kcal=3.14\times {10}^{6}J.$

Step: 3 Given information: (Part b)

A person uses for a long walk given are:$750kcal.$

To calculate the amount of energy expended on a walk is converting into kilojoules.

Step: 4 Converting into kilojoules: (Part b)

Use the appropriate conversion factor to convert energy into kilojoules. 

$1\mathrm{kcal}=1000\mathrm{cal}$

$1\mathrm{kcal}=4184\text{ joule }$

Changing  into kilojoules will be as, 

$750\mathrm{kcal}\times \left(\frac{4184\mathrm{J}}{1\mathrm{kcal}}\right)\times \left(\frac{1\mathrm{kJ}}{{10}^3\mathrm{J}}\right)=3.14\times {10}^3\mathrm{kJ}$

As a result,$750kcal==3.14\times {10}^3\mathrm{kJ}.$