Results 1 to 4 of 4

Thread: HSC 2019 Chemistry Marathon

  1. #1
    Cadet
    Join Date
    Sep 2018
    HSC
    N/A
    Gender
    Male
    Posts
    46
    Rep Power
    1

    HSC 2019 Chemistry Marathon

    Hey hey hey!

    Welcome to the HSC Chemistry Marathon if you sitting the HSC Chemistry Exam in 2019!

    The previous HSC Chemistry Marathon has already set out the rules of the chemistry marathon. So I am just going to copy the rules from the 2016 HSC Chemistry Marathon (old syllabus).

    HSC 2016 Chemistry Marathon

    "So, here are the rules:

    This thread is an open chain of questions between students. It works by answering a question then posting another question and allowing the cycle to repeat itself as this is used to test others!

    Just some simple rules:
    - Answer the question asked previously, before posting a new question.
    - After you have answered a question, post another question to keep the thread alive (or else I have to come in and post a new question)
    - try to allocate a number of marks for any question that you post.

    Tips:
    - It may help to write your answers on paper before typing them on this thread as it will mirror your exam.
    - You may post more than one question.
    - When possible, after questions have been answered, you can peer mark using the marking scheme.

    For future reference, please refrain from using this thread for help. Instead I'd suggest you make your own individual thread in the Chemistry Section of this forum if you want help.

    Also, please refrain from derailing this thread. If you want to talk about a specific topic or whatever to someone else, please do it via PM or have the conversation somewhere else as we want the marathon running smoothly"

    Let's #conquerhsc together! ~

  2. #2
    Cadet
    Join Date
    Sep 2018
    HSC
    N/A
    Gender
    Male
    Posts
    46
    Rep Power
    1

    Re: HSC 2019 Chemistry Marathon

    I will start off with three questions :>

    Question 1: Describe the similarities and difference between static and dynamic equilibria [5 marks]

    Question 2: Explain what an 'open system' and 'closed system' mean and provide an example of each. [4 marks]

    Question 3: Explain how collision theory is related to the rate of reaction for chemical reactions. [5 marks]


    Give em a shot! I will let you whether you got full marks or not and DM you with my feedback and solutions to the question right away! :>

    I will post the solutions here in 2 days. If you cannot wait that 'long' then just DM me. I will send it you xD

    Remember, after you submitted your answer after I have DM'ed you the solution, please post another question and I (or other students) will reply to it

    That way, you and I can learn and get lots of this marathon! :>

    Let's #conquerhsc together! 2019 HSC is going to be good year ^O^

  3. #3
    Cadet
    Join Date
    Sep 2018
    HSC
    N/A
    Gender
    Male
    Posts
    46
    Rep Power
    1

    Re: HSC 2019 Chemistry Marathon

    Response to Question 1:

    Similarities:
    The rate of the forward and reverse reaction are equal.
    The change in concentration for each species in the equilibrium reaction is constant.

    Differences:
    The rate of the forward and reverse reaction are zero for static equilibrium reactions.
    Static equilibrium reactions are considered irreversible due to the enormous energy required to convert reactants to products and products to reactants.



    Response to Question 2:

    A closed system is an environment that does not involve the exchange of matter with its external environment.

    All chemical reactions only involve the species in the system. While a closed system cannot exchange matter with the surrounding environment, it can exchange energy with the surrounding. An example of a closed system can be a sealed milk bottle sitting on a table.

    An open system is an environment that exchanges matter and energy with its ambient environment. A opened milk bottle sitting on a table.


    Response to Question 3:
    Collision theory states that reacting species must both have effective orientation and sufficient collision energy in order a chemical reaction to take place and for rate of reaction to be positive.

    The rate of reaction refers to the amount of reactants being converted into products over a set period of time.

    If the two criteria of the collision theory are not satisified, there will be a zero rate of reaction. This is because no reactants are being converted into products. Moreover, the amount of reacting species that satisfy (or does not satisfy) the two criteria will have an effect on the overall rate of reaction.


    New Question: Explain how Le Chatelier’s Principle can be used to predict how equilibrium position will shift when the concentrations of ions are varied when the Fe3+*+ SCN–*⇌ FeSCN2+*reaction is at equilibrium. [4 marks]

  4. #4
    Cadet
    Join Date
    Sep 2018
    HSC
    N/A
    Gender
    Male
    Posts
    46
    Rep Power
    1

    Re: HSC 2019 Chemistry Marathon

    Response to: "Explain how Le Chatelier’s Principle can be used to predict how equilibrium position will shift when the concentrations of ions are varied when the Fe3+*+ SCN–*⇌ FeSCN2+*reaction is at equilibrium. [4 marks]"

    In the event that there is a disturbance in the closed system affecting its equilibrium position, the system will counteract this change by shifting its equilibrium position which minimises the effect of the disturbance.

    When [Fe3+] increases, the system will shift its equilibrium position to the right to increase [FeSCN2+] in order to minimise the increased concentration of [Fe3+] as per Le Chatelier's Principle. Since FeSCN2+ ions have a crimson colour and Fe3+ ions have a yellow colour, the increase in [FeSCN2+] will the solution to appear red from yellow.

    Adding in more [SCN-] shift the equilibrium position to the right for the same reason as per Le Chatelier's Principle, resulting in the solution to turn red from yellow.

    According to Le Chatelier's Principle, increasing the concentration of [FeSCN2+] will cause the system to shift its equilibrium position to the left in order to minimise the increased concentration of [FeSCN2+] in solution. This will result in the solution changing its colour from red to yellow.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •