Chapter 2, Problem 5STP

Summary Introduction

Introduction:

SI units are used as standard units of measurement of seven base qualities such as distance, mass, time, quantity, etc. SI units are International System of Units.

Answer to Problem 5STP

Correct answer :

The correct answer is option (A) Number of particles in a substance.

Explanation of Solution

Explanation/justification for the correct answer :

Option (A). Number of particles in a substance. The mole is used as the measurement for amount of substance. It is defined as the exact number of particles in a number which is exactly 6.02214076 x 10²³ particles. These particles may be molecules, atoms or ions. So, the correct answer is option (A).

Explanation for incorrect answer :

Option (B) Compounds that make up a substance. When two or more elements are joined chemically to form a substance are known as compounds. When the elements are joined to form a new compound, they lose their individual properties but possess different properties from the elements. So, this is an incorrect answer.

Option (C)Number of elements ina substance. The number of elements in a substance is actually the number of protons in the nucleus. It is also referred as atomic number and is represented by Z. So, this is an incorrect answer.

Option (D)Total mass of the substance. Total mass of a substance is calculated as the sum of the mass of the two hydrogen atoms and one oxygen atom. So, this is an incorrect answer.