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### Half-life Clarification

Posted: **Mon Mar 11, 2019 2:42 pm**

by **Rogelio Bazan 1D**

To clarify my notes from the lecture, there is a different half-life equation based on which Reaction Order that we are dealing with? For example, zero order has its own half-life equation so on and so forth? Thank you.

### Re: Half-life Clarification

Posted: **Mon Mar 11, 2019 2:44 pm**

by **Emma Scholes 1L**

Yes. The half life equation depends on the reaction order.

### Re: Half-life Clarification

Posted: **Mon Mar 11, 2019 2:48 pm**

by **Brian Hom 2F**

Yes, each order has its own half life equation, because each order has different rates. However, in all the types of orders for reactions, the higher the k, the faster the rate.

### Re: Half-life Clarification

Posted: **Mon Mar 11, 2019 2:51 pm**

by **Melody P 2B**

Yes, because the half life equations are derived from the integrated rate laws. And the integrated rate laws differ in terms of reaction order.

This should help!

### Re: Half-life Clarification

Posted: **Mon Mar 11, 2019 2:51 pm**

by **Rachel-Weisz3C**

Yes. Each rate law has its own equation for 1/2 life. For example, the half-life for the 1st order is

and the half-life for 2nd order is

.

### Re: Half-life Clarification

Posted: **Mon Mar 11, 2019 2:52 pm**

by **MadelynNguyen1F**

Yes, and these are the equations I found:

For a zero order reaction A products , rate = k:

t½ = [Ao] / 2k

For a first order reaction A products , rate = k[A]:

t½ = 0.693 / k

For a second order reaction 2A products or A + B products (when [A] = [B]), rate = k[A]2:

t½ = 1 / k [Ao]