Chapter 3, Problem 79A

Interpretation Introduction

Interpretation:

The law used to compare CO and $C{O}_2$ needs to be explained. Also, the compound with greater mass percent needs to be determined without any calculation.

Concept introduction:

There are many ways of finding concentration of an element in a compound or a component in a mixture. Mass percent is one of those ways in which the concentration can be calculated.

The mass percent of an element in any compound is found as:

$\mathrm{mass}\%oftheelement=\frac{massoftheelement}{totalmassofcomp.}\times 100$

Answer to Problem 79A

Law of multiple proportion is used to compare CO and $C{O}_2$.

Mass percent of oxygen in CO and $C{O}_2$ is $57\%$ and $73\%$ respectively.

Explanation of Solution

Law of multiple proportions states that when two elements are combined to form more than one compound, the weight of one element that combines with the fixed weight of the other element are in a small simple ratio of whole numbers.

$\begin{array}{l}C+O_2\to C{O}_2\\ 2C+O_2\to 2CO\end{array}$

Mass percent of oxygen is calculated as:

$\mathrm{mass}\%ofO=\frac{massofO}{totalmassofcomp.}\times 100$

The mass percent of oxygen in $C{O}_2$ is greater than the mass percent in CO as there are two oxygen molecules that weighs heavier and hence the percentage of oxygen in $C{O}_2$ comes more.

Conclusion

Law of multiple proportion explains the relation, when the two reactant react to form more than one compounds. It states that when two elements are combined to form more than one compound, the weight of one element that combines with the fixed weight of the other element are in a small simple ratio of whole numbers.

The mass percent of the element that constitutes higher molecular weight in the compound, will be higher than the other element.