Chapter 2, Problem 4A

Interpretation Introduction

Interpretation: The given statement that compound always has the same composition needs to be explained.

Concept introduction: Chemical composition can be defined as the arrangement, ratio, and type of atoms in molecules of chemical substances. A property of the substance is determined by its chemical composition.

Answer to Problem 4A

All samples of a compound have the same composition means all samples have the same proportion, by mass, of the elements present in the compound.

Explanation of Solution

For example, consider ethanol $({\text{C}}_2{\text{H}}_5\text{OH)}$ . It has two carbon atoms, one oxygen atom, and six hydrogen atoms. If I have a compound that has a different number of oxygen atoms, it is something else.

If you make any variation like changing the number of atoms or replacing some atoms with other atoms then you have something different.

Take one more example, water is made up of two hydrogen (H) elements and one oxygen (O) atom. Whether it is bore-well or sea purified water samples will also have the same compositions in the same ratio.

Conclusion

All samples of a compound have the same composition means all samples have the same proportion, by mass, of the elements present in the compound.