Answer 1

Given: t_1/2 = 900 minutes

To find: λ

Formula: `lambda = 0.693/"t"_(1//2)`

Calculation: `lambda = 0.693/"t"_(1//2) = 0.693/(900 min)`

λ = 7.7 × 10^-4 min^-1 

Decay constant for ²⁴Na is 7.7 × 10^-4 min^-1.