Sodium-24 has a half-life of 15 hours. how many grams of a 900 g sample will remain after 90 hours A.28.125g B.14.0625 g C.7.5 g D.7.03125 g

Question

asked Jan 15, 2019 212k views

1 Answer

Totero · Answer 1 · 2019-01-21T15:15:21+0000

Answer: Option 'B' is correct.

Explanation:

Let the initial concentration be

$N_0=900\ g$

Let concentration after t= 90 hours be N

Since we have given that Sodium-24 has a half life of 15 hours i.e.

$t_{(1)/(2)}=15$

So, According to question,

$\text{ Number of half lives }=\frac{t}{t_{(1)/(2)}}\\\\\text{ Number of half lives }=(90)/(15)\\\\\text{ Number of half lives }=6$

As we know that

$(N)/(N_0)=((1)/(2))^n\\\\N=N_0* ((1)/(2))^n\\\\N=900* ((1)/(2))^6\\\\N=(900)/(64)\\\\N=14.0625\ g$

Hence, Option 'B' is correct.