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Edexcel IAL Chemistry Unit 01 - 26th of May, 2017 Watch

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    (Original post by Droneon)
    What's the question


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    Sorry that I don't have a question but Iam asking if you can explain the electrolysis of CuCrO4
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    (Original post by Aadha24)
    Sorry that I don't have a question but Iam asking if you can explain the electrolysis of CuCrO4
    K-Man_PhysCheM
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    (Original post by mr.holmes)
    hey
    can anyone please help me with these questions? i will really appreciate it!
    1. which of the following contains one mole of neutrons?
    A 1g of H1,1
    B 1g of C 12,6
    C 2g of Mg 24, 12
    D 2g of Ne 22,10

    2.
    10 g of Mg is added to 1dm3 of 1concentration copper (ii) sulfate solution and the mixture is stirred until no further reaction occurs.
    which of the following is a result of this reaction?
    A The resulting solution is colourless.
    B 10 g of copper is displaced.
    C 63.5 g of copper is displaced.
    D All the magnesium reacts.

    3.
    100 cm3 of hydrogen is mixed with 25 cm3
    of oxygen at a temperature of 150qC.
    The*gases react as shown in the equation below.
    2H2(g)+ O2(g) o 2H2O(g)
    The total volume of gas present at the end of the reaction is
    A 50 cm3
    B 100 cm3
    C 125 cm3
    D 150 cm3

    4.
    An experiment was carried out to measure the enthalpy change of the following reaction.
    NaOH(aq) + HCl(aq) ---------> NaCl(aq) + H2O(l)
    50 cm3 of hydrochloric acid was mixed with 50 cm3
    of sodium hydroxide solution.Each solution contained 0.10 mol solute. The temperature rise was 12C.
    Energy transferred (J) = mass of solution × 4.2 × change in temperature
    Assume the density of all solutions is 1.0 g cm–3.
    What is the enthalpy change of the reaction in kJ mol–1?

    A -(50 x4.2x12/0.1x 1000)
    .
    B -(50 x4.2x12/0.2x 1000)
    .
    C -(100 x4.2x12/0.1x 1000)
    .
    D -(100 x4.2x12/0.05x 1000)
    1. I believe the answer is C, mol of magnesium = 0.08333.... mol
    number of neutrons in magnesium is 12
    multiply mol of magnesium to number of neutrons to obtain your 1 mole of neutron.

    2. mol of magnesium =0.4167 mol
    mol of cuso4 = 1 mol
    looking at their moles , it is clear that cuso4 is in excess, so all the magnesium reacts, thus answer is D

    3. mol of H2 = 100/24000 = 1/240 mol
    mol of O2 = 25/24000 = 1/960 mol
    Reacting ratio H2: O2 = 2:1
    Moles of H2 is more than the double the moles of O2 (which is 1/480 mol), hence H2 is in excess, so 50 cm3 of unreacted H2 is present.
    So now we know O2 is the limiting reagent, we use mol of O2 to calculate mol of H2O.
    Reacting ratio O2: H2O = 1:2
    So mol of H2O = 1/960 * 2 = 1/480 mol
    1/480 mol * 24000 = 50 cm3
    Total vol. of gases at end of reaction = 50cm3 unreacted H2 + 50cm3 H2O = 100cm3
    Thus answer is B.

    4. Both Hydrochloric acid and Sodium hydroxide have equal moles and equal volume, so if they react together, 50cm3 + 50cm3 they essentially form 100cm3 of a neutral solution.
    Enthalpy change = Energy / mol
    mol of both solutions are 0.1
    thus enthalpy change = C (denominator times a 1000 because they want value in kJ)
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    @Aadha24
    I haven't looked at any electrochemistry beyond GCSE level, and I haven't encountered this reaction before, so I can't really help. I would suggest reading the textbook or reading this article: https://eic.rsc.org/exhibition-chemi...020064.article

    The reactions around the middle look to be of interest, especially reduction of chromate (VI) ion at anode and oxidation of copper (II) ions at cathode:

    CrO42- (aq) + 4H2O(l) + 3e- ⇌ Cr(OH)3 (s) + 5OH- (aq)
    Cu2+ (aq) + 2e- ⇌ Cu(s)
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    (Original post by Aadha24)
    Sorry that I don't have a question but Iam asking if you can explain the electrolysis of CuCrO4
    ur answer:
    (Original post by K-Man_PhysCheM)
    @Aadha24
    I haven't looked at any electrochemistry beyond GCSE level, and I haven't encountered this reaction before, so I can't really help. I would suggest reading the textbook or reading this article: https://eic.rsc.org/exhibition-chemi...020064.article

    The reactions around the middle look to be of interest, especially reduction of chromate (VI) ion at anode and oxidation of copper (II) ions at cathode:

    CrO42- (aq) + 4H2O(l) + 3e- ⇌ Cr(OH)3 (s) + 5OH- (aq)
    Cu2+ (aq) + 2e- ⇌ Cu(s)
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    (Original post by CaptainJackFail)
    1. I believe the answer is C, mol of magnesium = 0.08333.... mol
    number of neutrons in magnesium is 12
    multiply mol of magnesium to number of neutrons to obtain your 1 mole of neutron.

    2. mol of magnesium =0.4167 mol
    mol of cuso4 = 1 mol
    looking at their moles , it is clear that cuso4 is in excess, so all the magnesium reacts, thus answer is D

    3. mol of H2 = 100/24000 = 1/240 mol
    mol of O2 = 25/24000 = 1/960 mol
    Reacting ratio H2: O2 = 2:1
    Moles of H2 is more than the double the moles of O2 (which is 1/480 mol), hence H2 is in excess, so 50 cm3 of unreacted H2 is present.
    So now we know O2 is the limiting reagent, we use mol of O2 to calculate mol of H2O.
    Reacting ratio O2: H2O = 1:2
    So mol of H2O = 1/960 * 2 = 1/480 mol
    1/480 mol * 24000 = 50 cm3
    Total vol. of gases at end of reaction = 50cm3 unreacted H2 + 50cm3 H2O = 100cm3
    Thus answer is B.

    4. Both Hydrochloric acid and Sodium hydroxide have equal moles and equal volume, so if they react together, 50cm3 + 50cm3 they essentially form 100cm3 of a neutral solution.
    Enthalpy change = Energy / mol
    mol of both solutions are 0.1
    thus enthalpy change = C (denominator times a 1000 because they want value in kJ)
    Thank you so much for the help! i really appreciate it.
    could you please explain why the mole of the solution is 0.1 in the last question?
    thanks again
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    (Original post by mr.holmes)
    Thank you so much for the help! i really appreciate it.
    could you please explain why the mole of the solution is 0.1 in the last question?
    thanks again
    The question stated that there are 0.1 mol in each solution and if you look at equation both solutions are reacting in a 1:1 ratio, as well as the fact that both are equal in volume
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    can someone please explain how to find the number of atoms in 8.5g of CH2Cl2?
    thnks
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    (Original post by zooshan)
    can someone please explain how to find the number of atoms in 8.5g of CH2Cl2?
    thnks
    moles=8.5/rfm
    answerx6.02x10^ is (numberof atoms) which is 5
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    (Original post by zooshan)
    can someone please explain how to find the number of atoms in 8.5g of CH2Cl2?
    thnks
    Do it by using the formula , no. of moles x avagadros constant x no. of atoms in the molecule
    so no. of moles=0.1 (mass/m.mass)
    no. of atoms = 5 ( 1 C, 2H , 2Cl)
    now substitute , 0.1 x 6.02x10^23 x 5 = 3.01x10^23
    There u go
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    did anyone do January 2017?
    it was so hard!
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    (Original post by shahida sulaiman)
    Do it by using the formula , no. of moles x avagadros constant x no. of atoms in the molecule
    so no. of moles=0.1 (mass/m.mass)
    no. of atoms = 5 ( 1 C, 2H , 2Cl)
    now substitute , 0.1 x 6.02x10^23 x 5 = 3.01x10^23
    There u go
    thanks
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    (Original post by Reshyna)
    That's nice bro :thumbsup:
    But can you edit out my name, and type reshyna instead... plssss
    ok fine sis!!!!
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    (Original post by mr.holmes)
    did anyone do January 2017?
    it was so hard!
    How'd you construct your sentence in the first question of section B? about the bromine water?

    I'm thinking
    Before shaking the test tube, two layers, brown and colourless are seen.
    After shaking, the brown layer then turns colourless, and we see two colourless layers.
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    (Original post by CaptainJackFail)
    How'd you construct your sentence in the first question of section B? about the bromine water?

    I'm thinking
    Before shaking the aqueous layer, two layers, brown and colourless are seen.
    After shaking, the brown layer then turns colourless, and we see two colourless layers.
    i wrote it in this way:
    before shaking:
    the solution will settle into two layers brown and a colorless layer
    after shaking:
    a colorless solution will be observed.

    i wrote the answer in bulleted points. is it acceptable?
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    (Original post by mr.holmes)
    i wrote it in this way:
    before shaking:
    the solution will settle into two layers brown and a colorless layer
    after shaking:
    a colorless solution will be observed.

    i wrote the answer in bulleted points. is it acceptable?
    yes bullet points are acceptable..
    how about the last question in the june 16 paper about shale gas?
    how did u guys write out that answer?
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    (Original post by zooshan)
    yes bullet points are acceptable..
    how about the last question in the june 16 paper about shale gas?
    how did u guys write out that answer?
    i wrote that production of polymers will increase
    and i gave an example.
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    (Original post by mr.holmes)
    i wrote that production of polymers will increase
    and i gave an example.
    whats the reasoning behind ur answer?
    i wrote the same....
    am i the only one who hates these type of questions
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    how can we write an equation which represents the reaction for which the enthalpy change, H, is the
    mean bond energy of the C-F bond?

    i do not understand the concept of the mean bond enthalpy. are the products supposed to be 1 mole?
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    (Original post by mr.holmes)
    how can we write an equation which represents the reaction for which the enthalpy change, H, is the
    mean bond energy of the C-F bond?

    i do not understand the concept of the mean bond enthalpy. are the products supposed to be 1 mole?
    maybe this will help?
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