Overall order of the reaction A LEVEL CHEMISTRY
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've been told to use units to calculate the overall order of this reaction but I'm still confused at how to get the answer. Can someone pls help!!!
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've been told to use units to calculate the overall order of this reaction but I'm still confused at how to get the answer. Can someone pls help!!!
Reply 1
Hi, i believe the overall order would be 2.
Im not sure if this is the right way to do it but as the rate constant has the units of dm3mol-1s-1, it should mean that the rate (moldm-3s-1) is over 2 x (moldm-3).
I dont think i've explained it the best but if you're still confused i can try to upload an image that might explain it better.
Im not sure if this is the right way to do it but as the rate constant has the units of dm3mol-1s-1, it should mean that the rate (moldm-3s-1) is over 2 x (moldm-3).
I dont think i've explained it the best but if you're still confused i can try to upload an image that might explain it better.
Reply 2
Original post
by someoneSThe 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've been told to use units to calculate the overall order of this reaction but I'm still confused at how to get the answer. Can someone pls help!!!
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've been told to use units to calculate the overall order of this reaction but I'm still confused at how to get the answer. Can someone pls help!!!
The rate constant, k, is expressed in units of (dm^3 mol^-1 s^-1), while the rate itself is in units of (mol dm^-3 s^-1).
The rate law, which represents the concentrations of reactants, where [A and B], are just how concentrated our reactants, is used to calculate the rate:
which can be expressed as
(dm^3 mol^-1 s^-1) = (mol dm^-3 s^-1) / [(mol dm^-3)^n x (mol dm^-3)^m].
The concentration units are raised to their respective powers, with dm^3 on the left and dm^-3 raised to (m + n). The total order is (m + n).
By comparing the powers of dm and mol on both sides, the total order can be determined.
Here is my 2 cents!
Reply 3
Original post
by someoneSThe 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've been told to use units to calculate the overall order of this reaction but I'm still confused at how to get the answer. Can someone pls help!!!
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've been told to use units to calculate the overall order of this reaction but I'm still confused at how to get the answer. Can someone pls help!!!
The hint is in the units of the rate constant.
The rate itself must always be in mol dm^-3 s^-1, since it measures how concentrations vary with time.
The rate equation will take the form
Rate = k {HCl}^a {H2}^b
Where a and b are the respective orders of reaction for ICl and H2 and also a + b is the overall order of reaction (e.g the sum of the orders of reaction of all the reactants).
Subbing in only the units, we have
mol dm^-3 s^-1 = (mol^-1 dm^3 s^-1) x (mol dm^-3)^a x (mol dm^-3)^b
Dividing both sides by mol^-1 dm^3 s^-1 (or equivalently multiplying both sides by mol dm^-3 s) to get rid of the units of the rate constant:
mol^2 dm^-6 = (mol dm^-3)^a x (mol dm^-3)^b
Using index laws to clean up the right hand side:
mol^2 dm^-6 = (mol dm^-3)^(a + b)
We can rewrite the left hand side as a power of mol dm^-3 as follows
(mol dm^-3)^2 = (mol dm^-3)^(a + b)
So we have a + b = 2. That is to say the overall order of reaction is 2.
Note that curly brackets have been used to represent concentrations here. This is because for some reason, TSR doesn't seem to like it when square brackets are typed around H2, so the notation is erroneous. Please use square brackets to denote concentrations when answering exam questions in order to minimise the number of marks you lose needlessly.
(edited 11 months ago)
Quick Reply
Related discussions
- Chemistry Qs
- Alevel ocr a chem order graphs conc vs time
- Logarithms????
- OCR B Salters A Level Chemistry 2025 Advanced Article
- AQA Chemistry Electrode Potentials Conventional Representation Question
- ✨𝒂𝒂𝒇𝒊𝒚𝒂𝒉'𝒔 𝒈𝒚𝒈✨ - 𝑨𝑸𝑨 𝑨-𝒍𝒆𝒗𝒆𝒍 𝑪𝒉𝒆𝒎𝒊𝒔𝒕𝒓𝒚 🩵
- Chemistry Question AQA
- Y11 UKChO
- how to prepare for rsc chem olympiad?? chemistry help?
- Exam boards a level
- Higher Chemistry Crasher
- Chemistry Olympiad
- AQA A Level Chemistry - Kinetics Measuring Rate
- 3 or 4 A Levels for Psychology
- chemistry ocr a level redox question help
- Chemical engineering
- Entry requirements for Geology courses
- Sodium Thiosulfate and Hydrochloric Acid. Why is it zero order?
- IB Subject Choices
- CHemistry EPQ?
Latest
Trending
Last reply 3 months ago
AQA A level chemistry synthetic routes map - what is the best one to memorise?Last reply 8 months ago
AQA Chemistry Electrode Potentials Conventional Representation QuestionLast reply 10 months ago
OCR B Salters A Level Chemistry 2025 Advanced ArticleLast reply 11 months ago
Help with this chemistry question? (A2, acid-base equilibria)
How The Student Room is moderated
To keep The Student Room safe for everyone, we moderate posts that are added to the site.
