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  1. A

    Chemistry MCQ thread...

    C - HCO2H. Hydrogen bonding can only occur when an hydrogen atom is directly attached to a small and highly electronegative atom (F, N, O). In this case, one of the H atoms in the carboxylic acid group is attached to an oxygen atom.
  2. A

    Chemistry MCQ thread...

    Esters don't mix completely with water. The small esters are fairly soluble in water but solubility falls with chain length.
  3. A

    Chemistry MCQ thread...

    I think it's A, but I'm not completely sure.
  4. A

    Chemistry MCQ thread...

    I was wondering the same thing. This is what it says in the ER: "The most surprising response came in Q40, in which candidates were asked to identify those products of the hydrolysis of methyl butanoate, CH3CH2CH2CO2CH3, with NaOH (aq) that would be in a subsequent distillate. Whereas 80%...
  5. A

    Chemistry MCQ thread...

    Q9 - The choices we've been given are propane and 3 of its oxidation products. Every stage in the oxidation process will be exothermic, and therefore the earliest point in a sequence of oxidations will yield the highest energy release. The answer is B - propane. Or you could also use the bond...
  6. A

    Chemistry MCQ thread...

    No, just left and right. If you think about the definition, a neighbour is usually someone who lives next-door to another (to the left or right), not on top or below. ;p
  7. A

    Chemistry MCQ thread...

    The question means that the IE has to be higher than both the element that comes before it and the element that comes after it. In this case, the answer is B. Al has a second IE of 1820, higher than the element before it (Mg - 1450) and higher than the element after it (Si - 1580). I hope that...
  8. A

    Chemistry MCQ thread...

    Why can't it be D?
  9. A

    Chemistry MCQ thread...

    The intermediate is a carbocation. It has a positive charge so it's capable of accepting a lone pair of electrons. It's an electrophile.
  10. A

    Chemistry MCQ thread...

    Yeah, I think it's C too. Although deltaH is negative and the reaction is thermodynamically favourable, it's not kinetically feasible (activation energy's high and the reaction's very slow). You'd need a lot of energy to break the C-C covalent bonds and restructure the lattice (from...
  11. A

    Chemistry MCQ thread...

    Please can you explain why?
  12. A

    Chemistry MCQ thread...

    Oops, I typed it wrong. CH2ClCH=CHCl
  13. A

    Chemistry MCQ thread...

    No, what you wrote aren't free radicals. The question is asking about the different forms of X` produced.
  14. A

    Chemistry MCQ thread...

    The 7 isomers of C3H4Cl2 : 1. CH3CH=CCl2 2 & 3. CH3Cl=CHCl (this has a -cis and a -trans form) 4. CH2ClCCl=CH2 5 & 6. CH2Cl=CHCl (this also has a -cis and a -trans form) 7. CHCl2CH=CH2 I hope that made sense.
  15. A

    Chemistry MCQ thread...

    Yeah, it's C. But are those 3 forms of X` correct?
  16. A

    Chemistry MCQ thread...

    The answer's D, right? I'd explain but it's kinda difficult to type cis-trans isomers.. :X
  17. A

    Chemistry MCQ thread...

    I'm not entirely sure about this, but I just wanted to make sure. The different forms of X` are: R-CH2` R-CHCl` R-CCl2`
  18. A

    chem mcq...

    Isn't the answer B? The answer for May/June 2007 question 11, according to the mark scheme, is B.
  19. A

    Chemistry MCQ thread...

    Thanks Zishi, you really helped me out! Good luck with any exams you have left! (:
  20. A

    Chemistry MCQ thread...

    'kayy, last question! (for now xD). I get 38% when I do this. My calculation is: 1 mol ethanol gives 1 mol ester 46g ethanol gives 88g ester so 30g of ethanol should give (30/46) x 88 = 57.4g ester However, 22g are actually formed so the %age yield = (22/57.4) x 100 = 38% The actual answer is 50%.
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