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  1. X

    Chemistry MCQ thread...

    as you said, concentrated sulphuric acid is for dehyrdration. (CH3)3CCH2OH cannot undergo dehydration. - dehydration requires the alcohol to remove the -OH group from one carbon and another -H atom from the carbon next to it - (CH3)3CCH2OH cannot do this
  2. X

    chem mcq...

    for o/n 2007, why is ques 9 answer B?
  3. X

    Chemistry MCQ thread...

    C is wrong because it is formed at the temperature of combustion of the carbon!!! it should be at STANDARD CONDITIONS, 25'c , 1atm!!!
  4. X

    Chemistry MCQ thread...

    according to boyle's law, p1v1 = p2v2 so when the 2 flask connect together, the total volume is now 1 + 2 = 3dm3 using the formula above , for flask X - 1 x 2 = p x 3 - p = 2/3 for flask Y - 2 x 1 = p x 3 - p = 2/3 therefore, the total pressure after both flask connect is 2/3 + 2/3 = 4/ 3 so...
  5. X

    Chemistry MCQ thread...

    all A, B, C and D have high melting point. - graphite is an allotrope of carbon ( meaning the same element of different form ) - Aluminium chloride dissolves in water to give a very acidic solution / magnesium chloride dissolves partially water / chloride of lead and CCl4 do not dissolve in...
  6. X

    chem mcq...

    because the definition of enthalpy change of formation is '1 MOLE of compound is formed from its constituent element' u have to divide the enthalpy of ICl by 2. so that you get 1 mole which would give u an enthalpy of 7kJmol instead of 14kJmole
  7. X

    Chemistry MCQ thread...

    how is AlCl3 IONIC?!!! - AlCl3 is pure covalent - exists in simple molecular form - held together by weak VDW AlCl3 IS COVALENTLY BONDED!!!
  8. X

    Chemistry MCQ thread...

    AlCl3 and SiCl4 are a COVALENT COMPOUND! not ionic properties whatsoever. the question says ionic with some covalent character. this only happens when - the charge on the cation is large ( Mg > Na ) - the cation is small ( Mg < Na ) - the size of the anion is large since both anion are the...
  9. X

    The Ultimate AS Physics Thread

    one complete oscillation is 360' = 1 wavelength so half an oscillation is 180'. then 180' divide by 3 = 60' - the question made it really easy cause half an oscillation is 3 squares so 1 square = 60'.
  10. X

    The Ultimate AS Physics Thread

    even if you didn't use kirchoff's law which i happen to not understand here too, you will still get the answer. - all you need to do is use the formula is (a) to find the total resistance of the Q and the thermistor. - then use the normal parallel resistance formula and you will get the...
  11. X

    The Ultimate AS Physics Thread

    guys, can you help me with may/june 2008 ques 6b. i got everything alright its just the 2nd and the 3rd that i don't understand. thanks
  12. X

    Bio: smoking n diseases- help required

    epidemiological - smokers are 3 times more likely to die in middle age than non smokers - 90% of deaths from chronic obstructive pulmonary disease are attributed to smoking - 98% of people with emphysema are smokers. but seriously, don't even bother memorising, nobody is gonna ask you to list...
  13. X

    ~AS Bio doubts Here !!~

    2 forms : triglyceride + phospholipids triglyceride - made up of glycerol + 3 fatty acids, form by condensation - insoluble in water, but soluble in organic solvents - non-polar, hydrophobic - f(x) : storage for energy ( stores more energy than carbohydrate ) : as insulator against...
  14. X

    ~AS Bio doubts Here !!~

    - sucrose are loaded at the source into the companion cells. - H+ ions are pumped out of the companion cells - sucrose move into the companion cells through co-transporters - sucrose move into the companion cells via active transport - sucrose then move into the sieve tubes via the plasmodesmata...
  15. X

    ~AS Bio doubts Here !!~

    i know itz kinda late, but u should really read the marking schemes!
  16. X

    Bio: smoking n diseases- help required

    this one only normal comes out in paper 1. anyway, epidemiological evidence is like statistics reports experimental evidence are those stupid dogs and mice that got applied with carcinogens and ended up with cancers.
  17. X

    ~AS Bio doubts Here !!~

    from 2002 to 2010, everything seems to be on the same scale.
  18. X

    ~AS Bio doubts Here !!~

    - blood flowing into the lungs have higher partial pressure of CO2 and lower partial pressure of O2. - alveoli is higher in partial pressure of O2 and lower in partial pressure of CO2. - CO2 and oxygen moves down the concentration gradient. - O2 diffuses into the moist surface of the alveoli...
  19. X

    role of decomposers in nitrogen cycle and carbon cycle..?

    Re: role of decomposers in nitrogen cycle and carbon cycle.. decomposers breaks down starch, cellulose into glucose. ( glucose contains carbon hence returning carbon ) decomposers break down protein to amino acids, process know as deamination. the amino acids are then converted to ammonium...
  20. X

    bio...oncogene....?

    oncogenes are genes that are mutated by carcinogens which causes cancer - carcinogens cause mutations in genes - oncogenes which cause cancer is formed - the cancerous cells does not respond to signals and divides by mitosis uncontrollably - the cancerous cells grows bigger and becomes a tumour...
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