# Reaction Rates

The equation for the reaction of ICl and H2 is shown below.
2ICl (g) + H2(g) 2HCl (g) + I2(g)
The rate constant k for this reaction is 1.63 × 10−6 dm3 mol−1 s−1.
What is the overall order of the reaction?

A 0
B 1
C 2
D 3

I understand that you have to use the units but how?
(edited 9 months ago)
Original post by Incrediblezed
The equation for the reaction of ICl and H2 is shown below.
2ICl (g) + H2(g) 2HCl (g) + I2(g)
The rate constant k for this reaction is 1.63 × 10−6 dm3 mol−1 s−1.
What is the overall order of the reaction?

A 0
B 1
C 2
D 3

I understand that you have to use the units but how?

The rate of a chemical reaction is always measured in mol dm^-3 s^-1.

If you divide the units of the rate of a chemical reaction by the units of its rate constant, you will always get the units of concentration (mol dm^-3) raised to the power of the overall reaction order.

See what happens when you try this approach.
(edited 9 months ago)
Original post by Incrediblezed
The equation for the reaction of ICl and H2 is shown below.
2ICl (g) + H2(g) 2HCl (g) + I2(g)
The rate constant k for this reaction is 1.63 × 10−6 dm3 mol−1 s−1.
What is the overall order of the reaction?

A 0
B 1
C 2
D 3

I understand that you have to use the units but how?

k = Rate/[A]

k = dm3 mol-1 s-1
Rate = mol dm-3 s-1

Overall order = Rate / k
If you compare the units you realise overall order = 2
Original post by PixiePresents
k = Rate/[A]

k = dm3 mol-1 s-1
Rate = mol dm-3 s-1

Overall order = Rate / k
If you compare the units you realise overall order = 2

OHH okay thanks I understand now
Hi @Incrediblezed,