A gas containing doubly-charged ions flows to give an electric current of 0.64 A - AQA - A-Level Physics - Question 25 - 2018 - Paper 1

Since the ions are doubly charged, each ion contributes a charge of 2 elementary charges. The charge of one elementary charge (e) is approximately (1.6 \times 10^{-19} \text{ C}). Therefore, the charge contributed by one doubly charged ion is:

$Q_{ion} = 2 \times e = 2 \times 1.6 \times 10^{-19} = 3.2 \times 10^{-19} \text{ C}$

To find the number of ions (n) that pass a point, we use the formula:

$n = \frac{Q}{Q_{ion}}$

Substituting the values:

$n = \frac{38.4}{3.2 \times 10^{-19}} = 1.2 \times 10^{20}$

The number of ions that pass a point in 1.0 minute is (1.2 \times 10^{20}). Therefore, the correct option is:

C. 1.2 × 10²⁰