## Time Conversions

$\frac{d[R]}{dt}=-k[R]; \ln [R]=-kt + \ln [R]_{0}; t_{\frac{1}{2}}=\frac{0.693}{k}$

Mya Majewski 1L
Posts: 89
Joined: Fri Sep 25, 2015 3:00 am

### Time Conversions

For [A]=[A]oe^-kt, there seems to always be conversions associated with the -kt and time, do you convert the k or the t to equal the same units (minutes, seconds, hours) as one another?

Karan Thaker 2L
Posts: 75
Joined: Fri Sep 28, 2018 12:26 am

### Re: Time Conversions

Use the appropritate time conversions: 1 hr is 60 mins, 60 secs in 1 min, 24 hr in day, etc.Set up diagonal conversions to cancel units out and end in whatever time unit you need.

Yvonne Du
Posts: 64
Joined: Fri Sep 28, 2018 12:23 am

### Re: Time Conversions

Yes, just make sure that your units are consistent.

Mya Majewski 1L
Posts: 89
Joined: Fri Sep 25, 2015 3:00 am

### Re: Time Conversions

if your k is in min^-1 and your t is in seconds then what do you do?

805169754
Posts: 61
Joined: Fri Sep 28, 2018 12:19 am

### Re: Time Conversions

Mya Majewski 1L wrote:if your k is in min^-1 and your t is in seconds then what do you do?

You can convert either one as long as it matches/is consistent with the other. You should try to see if the question specifies in what units it wants the answer.

Ethan Breaux 2F
Posts: 63
Joined: Sat Sep 29, 2018 12:16 am

### Re: Time Conversions

always use the units that the question initially gives you unless stated otherwise. so yeah convert everything to one type of unit. and don't forget conversions between kJ and J (unrelated sidenote)

Claudia Luong 4K
Posts: 59
Joined: Fri Sep 28, 2018 12:25 am

### Re: Time Conversions

You can use any time unit as long as the same time unit is used for all values in the problem.

Abigail_Hagen2G
Posts: 107
Joined: Fri Aug 09, 2019 12:17 am

### Re: Time Conversions

So, it doesn't matter seconds or minutes as long as you have all the same units.

205405339
Posts: 77
Joined: Thu Jul 11, 2019 12:16 am

### Re: Time Conversions

both should have the same units. it does not really matter what unit it is as long as units match

kristi le 2F
Posts: 102
Joined: Thu Jul 11, 2019 12:15 am

### Re: Time Conversions

The units should be the same so that they will cancel out when doing calculations. Also, sometimes, the question will ask for the answer in a particular unit.