Question

A 10 gram sample of a substance that's used to detect explosives has a k-value of 0.1356.
Find the subtance's half-life, in days.round to the nearest tenth

Answer 1

please help

Answer 2

I will try my best ><. This is chemistry ?

Answer 3

no algebra

Answer 4

okay give me a minute and let me work it out

Answer 5

ok

Answer 6

are you still working it out?

Answer 7

lol yesh, I am questionable about my answer considering I am given no other variables but the constant an mass

Answer 8

I divided 10 by the k-value constant since this seem like rate of decay

Answer 9

10/0.1356

Answer 10

N=Noe^-kt
No=initial mass( at time t=0)
N=mass at time t
k=a positive constant that depends on the substance itself and on the units used to measure time
t=time, in days

Answer 11

@LiteLegacy

Answer 12

Sorry can't swing it I'm to unsure ~-~

Answer 13

But insert the value you have Like No=10 for the intial and and K-0.1356

Answer 14

can you tell me what you think it is?

Answer 15

@LiteLegacy

Answer 16

73.7 but that is highly wrong to me ><

Answer 17

@rational

Answer 18

@Loser66

Answer 19

@coolman500

Answer 20

it works as follows:

\[\frac{N}{N_o} = \frac {1}{2} = e^{- k t_{half}} \\ \ln ( \frac {1}{2} ) = -\ln ( 2 ) = - k t_{half} \\ t_{half} = \frac{\ln(2)}{k}\]

in summary
half life = ln(2)/k
AND
k = ln(2)/half life

here you get 5.1 days

the mass is a red herring, the half life for a kilo of the stuff should be the same as the half life for a gram.