Today, uranium contains $0.72 \%$ $235 \mathrm { U }$ (half-life = 0.70 billion years)and $99.28 \%$ $238 \mathrm { U }$ (half-life = 4.5 billion years). At a time 1.9 billion years ago, what was the fraction of $235 \mathrm { U }$ in uranium?

Question

Quizplus · Accepted Answer

To find the fraction of $235 \mathrm{U}$ 1.9 billion years ago, we use the decay formula: $N(t) = N_0 \times (1/2)^{t/T}$. For $235 \mathrm{U}$, $t = 1.9$ billion years and $T = 0.7$ billion years. Calculate the remaining fraction and compare it to the current fraction to find the initial fraction. The calculation shows that the fraction was approximately 3.53%.

Today, Uranium Contains 0.72%0.72 \%0.72% 235U235 \mathrm { U }235U (Half-Life = 0

Today, Uranium Contains $0.72 \%$ $235 \mathrm { U }$ (Half-Life = 0