Half-life given decay constant λ = 0.0693 h^-1. What is the half-life?

Half-life given decay constant λ = 0.0693 h^-1. What is the half-life?

• A. 5 h
• B. 10 h
• C. 20 h
• D. 100 h

Answer: (B)

For a first-order decay, the half-life is given by t1/2 = ln(2) / λ. With λ = 0.0693 h^-1, t1/2 = 0.693 / 0.0693 ≈ 10.0 hours. So the half-life is about 10 hours, which matches the option around 10 hours. If you check the other possibilities, a half-life of 5 hours would require a larger λ (~0.1386 h^-1), 20 hours would need a smaller λ (~0.03465 h^-1), and 100 hours would need a much smaller λ (~0.00693 h^-1). The given λ leads directly to roughly 10 hours.

For a first-order decay, the half-life is given by t1/2 = ln(2) / λ. With λ = 0.0693 h^-1, t1/2 = 0.693 / 0.0693 ≈ 10.0 hours. So the half-life is about 10 hours, which matches the option around 10 hours. If you check the other possibilities, a half-life of 5 hours would require a larger λ (0.1386 h^-1), 20 hours would need a smaller λ (0.03465 h^-1), and 100 hours would need a much smaller λ (~0.00693 h^-1). The given λ leads directly to roughly 10 hours.