The half-life of sodium-25 is 1.0 minute. Starting with 1 kg of this isotope, how
much will remain after half an hour?

Explanation:

k

=

0.693

t

1

2

On putting the value of half-life, we get:

k

=

0.693

1

=

0.693

(

min

)

−

1

First order rate law can be written as:

k

=

1

t

ln

a

0

a

t

Where,

k is rate constant

t is time required for decay

a

0

is the initial amount

a

t

is the amount left at time t.

On putting the values, we get:

0.693

=

1

30

ln

1

a

t

Therefore,

ln

1

a

t

=

0.693

×

30

a

t

=

9.35

×

10

−

10

k

g

9.35

×

10

−

10

k

g

it would be d. henry moseley

hope this !

and sorry if i'm late. have a good rest of your day! : d