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Size:  502.2 KBif the carbon carbon double bond is weaker than the c-c bond why does it have a greater bond enthalpy I.e. I don't why the answer to that question is that the carbon double bond is weaker
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    For a titration, is the acid always in the burette or is the solution of unknown just always the base (in flask)?
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    (Original post by n2697)
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Size:  502.2 KBif the carbon carbon double bond is weaker than the c-c bond why does it have a greater bond enthalpy I.e. I don't why the answer to that question is that the carbon double bond is weaker
    The C=C bond isn't weaker than the C-C bond, it is just less than twice as strong. This is because the pi bond in the C=C bond isn't as strong as the sigma bond which is present in both C=C bond and C-C bond.
    C=C has a higher bond enthalpy because more energy is required to break the bond
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    (Original post by Junaidc122)
    Mole H2O = mass / Mr = 1.8/18 =0.1
    Therefore to find the number of molecules of H2O, multiply Avagadro's:
    0.1 x 6.0 x10^23 = 6 x 10^22
    Next times by three , because there are 3 atoms per molecule, giving 1.8 x 10^23
    Hope this helped 😇


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    I forgot to multiply by three. That was very helpful, thank you

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    (Original post by TeaAndTextbooks)
    I forgot to multiply by three. That was very helpful, thank you

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    No problem


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Size:  213.1 KBAttachment 539139539141Another couple of questions i cant seemAttachment 539139539141539140 to get my head around. I was hoping someone could help out. I thought that yellow ppts only form when a carbonyl methyl group is present?
    thanks in advance
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    guys question,

    in mass spec why do we get different peaks for example Kr+1 and Kr+2

    and where are they drew on the mass spec graph
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    Anyone that can explain question 3


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    With the Hydroxides what are the test you do when its cloudy milky etc?? Quite confused and its not in the textbook.I'm referring to the part of the spec where it states "Students could test the solubility of Group 2 hydroxides by mixing solutions of soluble Group 2 salts with sodium hydroxide and record their results." vice versa for Sulfates.
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    Help please







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    Hey Guys! This is the official thread for tomorrow's Chem Unit 1 Edexcel exam. Make sure to discuss the paper there after you are done. Of course, wait for like half an hour after you are done coz some people may still be doing it. Good Luck!!

    http://www.thestudentroom.co.uk/show...0#post65221487
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    (Original post by Science_help)
    Lets see who gets this right.
    No using google or textbook btw.

    What temperature does diamond melt at ? nearest 100
    1200 degree?
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    I have an important question. Can someone sit the exam for me please?! :bigsmile:
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    (Original post by Enderbat1999)
    guys question,

    in mass spec why do we get different peaks for example Kr+1 and Kr+2

    and where are they drew on the mass spec graph
    you get various ions if you provide more energy to the sample then its first ioninsation energy.
    if kr+1 was m/z =84 on the graph, kr+2 would be 42, because x axis is is m/z, therefore if you have twice the charge the number halves
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    (Original post by GracelovesNeuro)
    With the Hydroxides what are the test you do when its cloudy milky etc?? Quite confused and its not in the textbook.I'm referring to the part of the spec where it states "Students could test the solubility of Group 2 hydroxides by mixing solutions of soluble Group 2 salts with sodium hydroxide and record their results." vice versa for Sulfates.
    From the reaction between unknown soluble group 2 salts and sodium hydroxide, you form a group 2 hydroxide (XCl2 + 2NaOH --> X(OH)2 + 2NaCl, where X is a group 2 element)
    And to test whether the group 2 hydroxide is produced from the reaction above, you dip a red litmus paper into the solution and if hydroxide ions are present, the paper will turn blue.
    The hydroxide ions make the solution alkaline hence you use the litmus paper.
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    (Original post by CERC)
    Ok, so i'm just going to type out what my revision guide says about this:


    1) The M+1 peak is a small peak one m/e value above the M+ peak. It is caused by the presence of ONE Carbon-13 atom in the molecular ion.

    2) A MAJOR peak at M+2 is caused by the presence of either Cl or Br atom in the molecule. Both Chlorine and Bromine have isotopes that differ by two mass units. Chlorine has 35 and 37 whilst Bromine has 79 and 81.

    IMPORTANT: If the ration of the M+ peak to the M+2 peak is 3:1 i.e. the M+ peak is three times as abundant as the M+2 peak, then a chlorine atom is present.

    However, the Bromine 79 and Bromine 81 have the same abundance, in a ration of 1:1. So, if the M+ peak has the same abundance as the M+2 peak then a Bromine atom is present in the molecule!


    Really hope this helps you!
    Yeah, that helped so much!!! Thank you
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    (Original post by PlayerBB)
    Yeah, that helped so much!!! Thank you
    Just so you know for edexcel you aren't expected to interpret mass specs that have m+1 m+2 peaks etc.
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    (Original post by samb1234)
    Just so you know for edexcel you aren't expected to interpret mass specs that have m+1 m+2 peaks etc.
    Really, well that's definitely great! But it was good to have an idea about them though

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    Why would there be a peak at 80 in mass spectrometry of Bromine? There are only two isotopes of bromine- 79 and 81 so why would there be peak at 80?
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    (Original post by damian21kk)
    Why would there be a peak at 80 in mass spectrometry of Bromine? There are only two isotopes of bromine- 79 and 81 so why would there be peak at 80?
    hard paper guys not good messed up on alot of the maths questions
 
 
 
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