Question 1

What is the SI unit of the amount of substance?

Accepted Answer

The SI unit of the amount of substance is the mole (symbol: mol). One mole contains exactly $6.02214076 	imes 10^{23}$ elementary entities.

Question 2

How many significant figures are present in $0.0025$?

Accepted Answer

Zeros preceding the first non-zero digit are not significant. Therefore, in $0.0025$, only '2' and '5' are significant digits, making the number of significant figures 2.

Question 3

Which of the following concentration terms is independent of temperature?

Accepted Answer

Molality is defined as the number of moles of solute per kilogram of solvent. Since mass does not change with temperature, molality is independent of temperature.

Question 4

Who proposed the Law of Conservation of Mass?

Accepted Answer

The Law of Conservation of Mass was proposed by Antoine Lavoisier in 1789. It states that matter can neither be created nor destroyed in a chemical reaction.

Question 5

What is the empirical formula of glucose ($C6H{12}O6$)?

Accepted Answer

The molecular formula of glucose is $C6H{12}O6$. Dividing the subscript numbers by their greatest common divisor (6) gives the simplest whole-number ratio $CH2O$.

Some Basic Concepts of Chemistry