Sodium-24 has a half-life of 15 hours. after 45 hours, how much sodium-24 will remain of an original 50.0-g sample? 5.56 g 6.25 g 16.7 g 25 g

option C

6.25 g

Explanation:

A = Ne

Here A is amount left after time t

         t is the time in hours

         N is the initial amount

         k is decay constant

Step 1

calculate constant value, k

Given in the question that, half life of sodium is 15 hours

So,

A = N/2(half the inital amount)

N/2 = Ne

N will be cancel on both sides

1/2 = e

Take logarithm on both sides

ln(1/2) = -k(15)

ln(0.5) = -k(15)

k = -ln(0.5)/15

k = 0.046

Step 2

calculate how much sodium will be left after 45hours

Given that original mass of the sample = 50 g

A = 50e

   = 6.25 g

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

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