Question

Find:

1. the total number and 
2. the total mass of neutrons in 7 mg of ¹⁴C.

(Assume that mass of a neutron = 1.675 × 10⁻²⁷ kg).

Answer 1

Number of atoms of ¹⁴C in 1 mole = 6.023 × 10²³

Since 1 atom of ¹⁴C contains (14 − 6) i.e., 8 neutrons, the number of neutrons in 14 g of ¹⁴C is (6.023 × 10²³) × 8.

Or, 14 g of ¹⁴C contains (6.022 × 10²³ × 8) neutrons.

Number of neutrons in 7 mg

= `(6.022 xx 10^(23)xx8xx7  "mg")/(1400  "mg")`

= 2.4092 × 10²¹