Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta

Chemistry A-Level rates question! watch

Announcements
    • Thread Starter
    Offline

    1
    ReputationRep:
    The question:

    The activation energy for the forward reaction is 184 kJ mol−1.
    2HI(g) U H2(g) + I2(g)

    At 700 K, the rate constant is 2.32 × 10−3 dm3
    mol−1 s−1.

    Calculate the rate constant at 800 K and give your answer to three significant figures.
    You should not attempt to use any graphical method to answer this question.
    The Arrhenius equation is

    In k = − Ea/R × 1/T + A
    [Gas constant, R = 8.31 J mol−1 K−1 and A is a constant]
    Offline

    12
    ReputationRep:
    What you want to do is use the equation and the data given at 700 to calculate a value for A.
    So, you'd do ln(2.32x10^-3) = 184000/8.31 x 1/700 + A and rearrange that to calculate A.
    Once you've got a value for A, write out the equation again, using the activation energy given, the value for A, and the temperature given. This will allow you to calculate lnk.
    Once you have lnk, do e^lnk to find k (I'm not sure about this step but I think that's right).
    It's a kind of strange question, took me a while to get my head around it.
    • Thread Starter
    Offline

    1
    ReputationRep:
    So I did it and got something like 0.121 and I think its wrong. What did you get out of interest?
 
 
 
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?
Help with your A-levels

All the essentials

The adventure begins mug

Student life: what to expect

What it's really like going to uni

Rosette

Essay expert

Learn to write like a pro with our ultimate essay guide.

Uni match

Uni match

Our tool will help you find the perfect course for you

Study planner

Create a study plan

Get your head around what you need to do and when with the study planner tool.

Study planner

Resources by subject

Everything from mind maps to class notes.

Hands typing

Degrees without fees

Discover more about degree-level apprenticeships.

A student doing homework

Study tips from A* students

Students who got top grades in their A-levels share their secrets

Study help links and info

Can you help? Study help unanswered threadsRules and posting guidelines

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.