Question

PLEASE HELP 20 POINTS

Answer 1

Hello!

A sample of Bromine-82 begins at 80 mL. We are given that this value will decrease by half of its current amount every 35 hours. First, we'll determine the number of times that 35 goes into 140. This will reveal the number of times we should divide the sample by 2:

140 ÷ 35 = 4

We have now proven that there are 4 periods of 35 hours in 140 hours. This means that we will divide the sample in half a total of 4 times, as follows:

1. 80 ÷ 2 = 40
2. 40 ÷ 2 = 20
3. 20 ÷ 2 = 10
4. 10 ÷ 2 = 5

We have now proven that an 80 mL sample of Bromine-82 will be reduced to only 5 mL after 140 hours. Therefore, the correct answer is 5 mL.

I hope this helps!

Answer 2

To solve this problem, we have to use the half-life formula, where A represents the remaining amount, P is the initial amount, t is the time that has passed, and h is the substance's half-life:

$A = P( \frac{1}{2} )^{\frac{t}{h} }$

This is what it looks like with the values from this scenario plugged in:

$A = 80( \frac{1}{2} )^{\frac{140}{35} } \\ A = 5$

There are 5 mL of the 80 mL Bromine sample left after 140 hours.