Select the correct answer. A scientist has 20 grams of the radioactive isotope sodium-24. The isotope decays exponentially as
shown in the table.
Time (hours)
Mass (grams)
5
15.9
10
12.6
15
10
20
7.9
25
6.3
30
5
Approximately what will the mass of the isotope be after 45 hours?
А. 1.5 grams
B. 2.5 grams
C. 3.5 grams
D. 4.5 grams

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)

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step-by-step explanation: