Question

how many water molecules are in 5.2 moles of water?
5.2
3.1 × 10²⁴
8.638 × 10⁻²⁴
6.02 × 10²³

Explanation:

Step1: Recall Avogadro's number

Avogadro's number is \( 6.02 \times 10^{23} \) molecules per mole. This means that 1 mole of any substance contains \( 6.02 \times 10^{23} \) particles (in this case, water molecules).

Step2: Calculate the number of molecules

To find the number of water molecules in 5.2 moles, we multiply the number of moles by Avogadro's number. So the formula is: Number of molecules \( = \) moles \( \times \) Avogadro's number.
Substituting the values, we get: \( 5.2 \times 6.02 \times 10^{23} \)
First, calculate \( 5.2 \times 6.02 = 31.304 \)
Then, \( 31.304 \times 10^{23} = 3.1304 \times 10^{24} \approx 3.1 \times 10^{24} \) (rounded to two significant figures as 5.2 has two significant figures)

Answer:

\( 3.1 \times 10^{24} \) (corresponding to the option: 3.1 × 10²⁴)