Which of the following is the correct representation of number of atoms?

(given mass/molar mass) × Avogadro number

The correct answer is option 1. (given mass/molar mass) × Avogadro number.

The formula \((\text{given mass/molar mass}) \times \text{Avogadro number}\) represents the calculation of the number of atoms in a substance based on the given mass, the molar mass of the substance, and Avogadro's number.

Let us break down the components of the formula:

1. Given mass: This is the mass of the substance for which you want to calculate the number of atoms. It is represented as \(\text{given mass}\).

2. Molar mass: The molar mass is the mass of one mole of a substance and is expressed in grams per mole (g/mol). It is represented as \(\text{molar mass}\).

3. Avogadro's number: Avogadro's number (approximately \(6.022 \times 10^{23}\)) is the number of atoms, ions, or molecules in one mole of a substance. It is represented as \(\text{Avogadro number}\).

The formula essentially states that to find the number of atoms, you divide the given mass of the substance by its molar mass to get the moles of the substance and then multiply by Avogadro's number to convert moles to the number of atoms.

Mathematically, the formula is:

\[ \text{Number of atoms} = \frac{\text{Given mass}}{\text{Molar mass}} \times \text{Avogadro number} \]

This formula is particularly useful in chemistry when working with quantities of atoms or molecules in a sample based on the known mass and molar mass of a substance.