Chapter 2, Problem 2.14P

(a)

Interpretation Introduction

Interpretation:

Whether the statement “a sample of potassium chloride from Chile contains the same percent by mass of potassium as one from Poland” obeys the law of mass conservation, the law of definite composition or the law of multiple proportions is to be determined.

Concept introduction:

The law of mass conservation - Introduced by the famous French chemist Antoine Lavoisier, the law states that there is no change in the total mass of the substances that go into any physical or chemical reaction.

The law of definite composition - This law can be defined as; a particular compound maintains an exact universal proportion of elements in its composition, irrespective of the source. The proposal for this law was made by Joseph Proust.

The multiple proportions law - The ratio of the weights of an element with variable mass is small whole numbers when it forms more than one compound by combining with an element with fixed weight.

(b)

Interpretation Introduction

Interpretation:

Whether the statement “a flashbulb contains magnesium and oxygen before use and magnesium oxide afterward, but its mass does not change”obeys the law of mass conservation, law of definite composition or the law of multiple proportions is to be determined.

Concept introduction:

The law of mass conservation - Introduced by the famous French chemist Antoine Lavoisier, the law states that there is no change in the total mass of the substances that go into any physical or chemical reaction.

The law of definite composition - This law can be defined as; a particular compound maintains an exact universal proportion of elements in its composition, irrespective of the source. The proposal for this law was made by Joseph Proust.

The multiple proportions law - The ratio of the weights of an element with variable mass is small whole numbers when it forms more than one compound by combining with an element with fixed weight.

(c)

Interpretation Introduction

Interpretation:

Whether the statement “arsenic and oxygen form one compound that is $65.2$ mass % arsenic and another that is $75.8$ mass % arsenic” obeys the law of mass conservation, law of definite composition or the law of multiple proportions is to be determined.

Concept introduction:

The law of mass conservation - Introduced by the famous French chemist Antoine Lavoisier, the law states that there is no change in the total mass of the substances that go into any physical or chemical reaction.

The law of definite composition - This law can be defined as; a particular compound maintains an exact universal proportion of elements in its composition, irrespective of the source. The proposal for this law was made by Joseph Proust.

The multiple proportions law - The ratio of the weights of an element with variable mass is small whole numbers when it forms more than one compound by combining with an element with fixed weight.

The mass fraction of an element in a compound is defined as the ratio of the sum of the masses of all the atoms of that element to that of the mass of one mole of compound.

$\text{Mass fraction of X}=\frac{\text{Mass of element X in compound A }}{\text{mass of compound A}}$

Mass percent of an element represents the percentage concentration of that element in a compound. It is equal to the mass fraction expressed as a percentage. The general formula to calculate the mass percent of an element A in a compound is as follows:

$\begin{array}{c}\text{Mass \% of element A}=\left(\frac{\text{Mass of element X in compound A }}{\text{mass of compound A}}\right)\left(100\right)\\ =\left(\text{Mass fraction of A}\right)\left(100\right)\end{array}$