Question

How many moles are 1.20x10 to the 25 power atoms of phosphorous

Answer 1

The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities (e.g., atoms, molecules, ions, electrons) as there are atoms in 12 grams of pure carbon-12 ( $^{12}\mathrm{C}$ ), the isotope of carbon with atomic weight 12. This corresponds to a value of $6.02214179(30)\times 10^{23}$ elementary entities of the substance. It is one of the base units in the International System of Units, and has the unit symbol mole.

1 mole of phosphorous $(P_4)$ contains 6.02214179(30) $\times 10^{23}$ molecules of $P_4$ . Each molecule of $P_4$ contains 4 atoms of phosphorous (P). Than 1 mole of phosphorous $(P_4)$ contains

$$6.02 \times 10^{23} \cdot 4 = 24.08 \times 10^{23} \text{ atoms}$$

Then $1.20 \times 10^{25}$ atoms of phosphorous (P) are

$$\frac{1.20 \times 10^{25}}{24.08 \times 10^{23}} = 5 \text{ moles of } P_4$$

Answer: 5 moles of $\mathbf{P}_4$ or 20 moles of $\mathbf{P}$ .