Determining Order


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805312064
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Joined: Thu Jul 11, 2019 12:16 am

Determining Order

Postby 805312064 » Mon Mar 09, 2020 11:21 pm

If we are not given a graph, how do you determine the order of a reaction? Do we have to write out all the reaction mechanism steps?

jisulee1C
Posts: 149
Joined: Thu Jul 25, 2019 12:17 am

Re: Determining Order

Postby jisulee1C » Tue Mar 10, 2020 1:47 am

It depends on how the problem is given to you. If there is the chart, with different concentrations and rates you can determine the order with respect to a reactant. Or if the rate constant is given in units you can determine the overall reaction order.

Vincent Leong 2B
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Joined: Fri Aug 09, 2019 12:15 am

Re: Determining Order

Postby Vincent Leong 2B » Tue Mar 10, 2020 10:36 am

The rate constant and elementary rxns can determine rate order.

Martina
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Joined: Thu Jul 25, 2019 12:16 am

Re: Determining Order

Postby Martina » Wed Mar 11, 2020 3:32 pm

You can also look at units of the rate constant if it is given and be able to tell what the order is.

Maika Ngoie 1B
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Joined: Fri Aug 02, 2019 12:16 am

Re: Determining Order

Postby Maika Ngoie 1B » Wed Mar 11, 2020 4:24 pm

Martina wrote:You can also look at units of the rate constant if it is given and be able to tell what the order is.


Yes! for zero order reactions the units are M/s. First order is s^-1, and second order is 1/M.s.

Julie_Reyes1B
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Re: Determining Order

Postby Julie_Reyes1B » Wed Mar 11, 2020 4:33 pm

Maika Ngoie 1B wrote:
Martina wrote:You can also look at units of the rate constant if it is given and be able to tell what the order is.


Yes! for zero order reactions the units are M/s. First order is s^-1, and second order is 1/M.s.

The way that I remember this is that rate is in the units M/s, then when you solve for k you have to divide by the concentration of the reactant. 0 order is [A]^0 which is 1, so you do not divide by anything and K will still have the units of M/s. 1st order has [A]^1 with units of M, so when you divide the units cancel and you are left with 1/s. 2nd order has [A]^2 with units of M^2. so when you divide by M^2 the result is 1/mS

005384106
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Joined: Sat Aug 24, 2019 12:16 am

Re: Determining Order

Postby 005384106 » Wed Mar 11, 2020 4:46 pm

Does the larger the order mean that the more collisions will occur?

Michelle Xie 2B
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Joined: Sat Aug 17, 2019 12:18 am

Re: Determining Order

Postby Michelle Xie 2B » Fri Mar 13, 2020 5:29 pm

You can look at units of rate constant for the orders of each reactant and add them together.


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