# Kinetics

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Hey

can someone explain to me how to work out the order of relation with respect to A and C? I know B is order one as you compare exp 1 and 2 (x4)

i get confused when two reactants change at the same time

thanks

can someone explain to me how to work out the order of relation with respect to A and C? I know B is order one as you compare exp 1 and 2 (x4)

i get confused when two reactants change at the same time

thanks

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#2

B is order 1 if you look at exp 1 and 2. Multiplying B by 4 multiplies the RR by 4.

A is order 2 because if you multiply A by two, the RR is multiplied by 4. For exp 1 and 3, B is multiplied by 8, so dividing the RR and B by 8, you see that dividing A by 2 divides the RR by 4.

For C look at exp 3 and 4. A is constant so can be ignored. B and C are variable. (0.3/0.8)=0.375

You can now multiply B in exp 3 by 0.375 and RR in exp 3 by 0.375, this gives

0.1, 0.30, 0.40, 0.6 x 10

From this you can work out the order with respect to C.

A is order 2 because if you multiply A by two, the RR is multiplied by 4. For exp 1 and 3, B is multiplied by 8, so dividing the RR and B by 8, you see that dividing A by 2 divides the RR by 4.

For C look at exp 3 and 4. A is constant so can be ignored. B and C are variable. (0.3/0.8)=0.375

You can now multiply B in exp 3 by 0.375 and RR in exp 3 by 0.375, this gives

0.1, 0.30, 0.40, 0.6 x 10

^{-3}From this you can work out the order with respect to C.

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(Original post by

B is order 1 if you look at exp 1 and 2. Multiplying B by 4 multiplies the RR by 4.

A is order 2 because if you multiply A by two, the RR is multiplied by 4. For exp 1 and 3, B is multiplied by 8, so dividing the RR and B by 8, you see that dividing A by 2 divides the RR by 4.

For C look at exp 3 and 4. A is constant so can be ignored. B and C are variable. (0.3/0.8)=0.375

You can now multiply B in exp 3 by 0.375 and RR in exp 3 by 0.375, this gives

0.1, 0.30, 0.40, 0.6 x 10

From this you can work out the order with respect to C.

**morgan8002**)B is order 1 if you look at exp 1 and 2. Multiplying B by 4 multiplies the RR by 4.

A is order 2 because if you multiply A by two, the RR is multiplied by 4. For exp 1 and 3, B is multiplied by 8, so dividing the RR and B by 8, you see that dividing A by 2 divides the RR by 4.

For C look at exp 3 and 4. A is constant so can be ignored. B and C are variable. (0.3/0.8)=0.375

You can now multiply B in exp 3 by 0.375 and RR in exp 3 by 0.375, this gives

0.1, 0.30, 0.40, 0.6 x 10

^{-3}From this you can work out the order with respect to C.

How do you know what is the constant? Is it always order 2?

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#4

(Original post by

Thank you! I've worked out that C has 0 order (?)

How do you know what is the constant? Is it always order 2?

**Alltimesarah**)Thank you! I've worked out that C has 0 order (?)

How do you know what is the constant? Is it always order 2?

The rate constant has order 0 because it is a constant.

The units of the rate constant are dm

^{6}mol

^{-1}s

^{-1}.

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#5

(Original post by

Yes I get A: 2, B: 1, C: 0.

The rate constant has order 0 because it is a constant.

The units of the rate constant are dm

**morgan8002**)Yes I get A: 2, B: 1, C: 0.

The rate constant has order 0 because it is a constant.

The units of the rate constant are dm

^{6}mol^{-1}s^{-1}.
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#6

(Original post by

The rate constant does not have an order, but if it did it would be 1 not 0 as any quantity raised to the power of 0 is 1 ...

**charco**)The rate constant does not have an order, but if it did it would be 1 not 0 as any quantity raised to the power of 0 is 1 ...

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#7

(Original post by

Any constant has order 0. If it had order 1 that would imply that it changed with respect to another variable.

**morgan8002**)Any constant has order 0. If it had order 1 that would imply that it changed with respect to another variable.

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#8

(Original post by

If a constant has order zero then it must equal 1.

**charco**)If a constant has order zero then it must equal 1.

^{2}has order 2, x is order 1, 1 is order 0, x

^{-1}has order -1 and so on.

Any constant can be considered a variable to the power of 0 multiplied by a coefficient.

It could not be order 1 as this would mean it changes as the variable changes, which would have significant consequences for the rate equation.

This is all assuming constant temperature.

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#9

(Original post by

Consider a polynomial. x

Any constant can be considered a variable to the power of 0 multiplied by a coefficient.

It could not be order 1 as this would mean it changes as the variable changes, which would have significant consequences for the rate equation.

This is all assuming constant temperature.

**morgan8002**)Consider a polynomial. x

^{2}has order 2, x is order 1, 1 is order 0, x^{-1}has order -1 and so on.Any constant can be considered a variable to the power of 0 multiplied by a coefficient.

It could not be order 1 as this would mean it changes as the variable changes, which would have significant consequences for the rate equation.

This is all assuming constant temperature.

It is meaningless to talk about order with respect to the rate constant.

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#10

(Original post by

A variable to the power of 0 multiplied by a coefficient is just saying 1 x coefficient. The coefficient IS the constant!

It is meaningless to talk about order with respect to the rate constant.

**charco**)A variable to the power of 0 multiplied by a coefficient is just saying 1 x coefficient. The coefficient IS the constant!

It is meaningless to talk about order with respect to the rate constant.

^{n}, where x is some variable. As the rate constant is always constant within the constraints of the question, n = 0, so the order is 0.

I think I see where you're coming from now. The order of the rate equation with respect to the rate constant is 1 but the order of the rate constant with respect to any other variable is 0. I think we were arguing over different things.

I do agree that it is pointless to talk about the order of the rate constant though.

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#11

**morgan8002**)

Any order n would mean that k = ax

^{n}, where x is some variable. As the rate constant is always constant within the constraints of the question, n = 0, so the order is 0.

I think I see where you're coming from now. The order of the rate equation with respect to the rate constant is 1 but the order of the rate constant with respect to any other variable is 0. I think we were arguing over different things.

I do agree that it is pointless to talk about the order of the rate constant though.

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