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  1. J

    Physics: Post your doubts here!

    Can anyone explain Answer is 2 and 3. Why? And Answer is D. Is it because it is impossible to be 0A current when there is max PD?
  2. J

    Physics: Post your doubts here!

    Answer is C, anyone explain? :o I really don't get this one, help anyone, answer is D
  3. J

    Physics: Post your doubts here!

    Answer is C. Always see this question, but never really understands it. Anyone explain? Answer B
  4. J

    Physics: Post your doubts here!

    speed 33 m s^–1 density of the air is 1.2 kg m^–3. The wall has an area of 12 m^2 What is the force? First u relate with ur data givien, So to relate Density = mass/volume How u get volume from data? The only way is to to relate speed and area. Speed multiply with area 33 X 12 = 396m^3 s^-1...
  5. J

    Chemistry: Post your doubts here!

    Hmmmm, I guess it is said in book and notes, adding PCl5 or PI3 is not needed with heat and reflux. But other need high temp or heat in reflux, don't really know if this helps sorry :/
  6. J

    Chemistry: Post your doubts here!

    Answer is D as it is reaction between ketone and 24 DNPH, which is able to done without heating (:
  7. J

    Chemistry: Post your doubts here!

    Which statements are true for an SN2 reaction? 1 One bond is broken as another bond is formed. 2 The formation of a transition state involves the collision of two molecules or ions. 3 A carbon atom in the transition state is bonded, either fully or partially, to five other atoms. Answer is...
  8. J

    Chemistry: Post your doubts here!

    1) Bond energy of HCl is higher than HBr, hence will has a high enthalpy change for HCl compare to HBr. 2) HBr bond energy higher tha HI, as if HBr formed, harder to form back to H2 and Br2, but it is easier for HI to form back H2 and I2, hence the Kp for HBr is higher than HI. 3) it is wrong as...
  9. J

    Chemistry: Post your doubts here!

    Which mixtures, on heating, produce the gas ND3? [D = an isotope of hydrogen] 1 CaO(s) and ND4Cl(s) 2 CH3CN and NaOD in D2O 3 NDH3Cl and NaOD in D2O Need help with this question Answer is 1 and 2 only. Why no 3?
  10. J

    AS Biology P1 MCQs Preparation Thread

    Omg, thank you so much!!! :D appreciate ur help!
  11. J

    AS Biology P1 MCQs Preparation Thread

    The following events occur during transcription. 1 Bonds break between complementary bases. 2 Bonds form between complementary bases. 3 Sugar-phosphate bonds form. 4 Free nucleotides pair with complementary nucleotides. Before the mRNA leaves the nucleus, which events will have occurred twice...
  12. J

    A level Biology: Post your doubts here!

    The following events occur during transcription. 1 Bonds break between complementary bases. 2 Bonds form between complementary bases. 3 Sugar-phosphate bonds form. 4 Free nucleotides pair with complementary nucleotides. Before the mRNA leaves the nucleus, which events will have occurred twice...
  13. J

    A level Biology: Post your doubts here!

    Omg, thank you SO MUCH!!!!! :D really appreciate your help
  14. J

    A level Biology: Post your doubts here!

    Some babies are born with a hole between the right and left atria. These newly born babies are found to have an increased number of red blood cells. What is the reason for this increase? A More blood is needed because it is pumped faster. B Newly born babies’ haemoglobin has a higher...
  15. J

    A level Biology: Post your doubts here!

    Answer is D. Can Anyone explain? Answer is D, why? :O
  16. J

    Physics: Post your doubts here!

    It's not from cm^3 to dm^3. It is from cm^-3 to m^3, cause u are converting to SI unit, that's why is m^3.
  17. J

    Chemistry: Post your doubts here!

    Which pairs of homologous series have the same C:H ratio in their general formulae? 1 aldehydes and ketones 2 carboxylic acids and esters 3 alkenes and ketones Answer is 1,2,3 Help :O
  18. J

    Chemistry: Post your doubts here!

    I chose A, why cant? Answer is B Answer is D, I understand why it is structural isomer, but donno why osmotic pressure increase. Answer is A. Why?? :eek:
  19. J

    Chemistry: Post your doubts here!

    The products obtained by cracking an alkane, X, are methane, ethene and propene. The mole fraction of ethene in the products is 0.5. What is the identity of X? A C6H14 B C8H18 C C9H20 D C11H24 Answer is B. I don't really understand the question, what does it mean the mole fraction of...
  20. J

    Chemistry: Post your doubts here!

    Which reaction will give 2-chloropropane in the best yield? A propane gas with chlorine gas in the presence of ultraviolet light B propan-2-ol with dilute NaCl (aq) C propan-2-ol with SOCl 2 D propene with dilute HCl (aq) I chose D, why cannot? Answer is C.
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