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  1. Mathemagical

    Chemistry: Post your doubts here!

    A nucleophile is a chemical species which donates an electron pair to an electrophile. Therefore, it must have a lone pair of electrons to do this.
  2. Mathemagical

    Chemistry: Post your doubts here!

    Yes, I got the same answers too. Where did you get these questions from?
  3. Mathemagical

    Chemistry: Post your doubts here!

    Ammonia has hydrogen bonding, which is the strongest intramolecular bond, so it is the least ideal.
  4. Mathemagical

    Physics: Post your doubts here!

    Liquids can flow due to their molecular characteristics. The bonds holding the liquid molecules together are relatively weak and therefore the molecules can move over one another.
  5. Mathemagical

    Chemistry: Post your doubts here!

    No worries, always glad to help.
  6. Mathemagical

    9701/11/O/N/12

    The answer is A. Let n be 3. The compound would be XY3, so the reaction would look like this: XY3 --> X + 3Y From this, we can see that 3 X-Y bonds are broken, so the bond enthalpy of X-Y would be the reaction enthalpy divided by 3. Substituting any value of n would yield the same result, so...
  7. Mathemagical

    physics practical coming up !!

    Hey, I have just posted a thread with notes and tips for the practical paper. Hope you find it useful! http://tinyurl.com/nzzozst
  8. Mathemagical

    Physics Practical Paper 3 Notes and Tips

    Hello guys, I know many of you will be sitting for this paper next week and are probably wondering how to revise, so I have compiled a few tips and notes for all of you. Enjoy! 1. During the test, read the question and all information given carefully. Make sure that you understand the...
  9. Mathemagical

    Physics: Post your doubts here!

    Question 24: Imagine the wave moving from left to right. Point C would be moving upwards with maximum speed because it precedes a crest. Question 6: Read the question carefully. The question asks for average velocity, not average speed. Since the graph clearly shows motion in the opposite...
  10. Mathemagical

    Chemistry: Post your doubts here!

    Check the structure carefully. The compound is not symmetrical so C would not be the same.
  11. Mathemagical

    Chemistry: Post your doubts here!

    That's correct. Carbon has 2 electrons in the p-orbital and the chloride ion has 4 electrons in the p orbital. However, both have 2 unpaired electrons in the orbital, so Option 3 is correct.
  12. Mathemagical

    Chemistry: Post your doubts here!

    Ethanoic acid dissociates into CH3COO- and H+ ions. Calcium forms Ca2+ ions, so 1 mol of Ca2+ ions will combine with 2 moles of CH3COO- ions.
  13. Mathemagical

    Chemistry: Post your doubts here!

    One on the CH3 group on the far left, one on the CH2 beside it, the other on either one of the CH3 groups attached to the central carbon atom.
  14. Mathemagical

    Chemistry: Post your doubts here!

    Doubt it. Calcium carbonate decomposes into calcium oxide and carbon dioxide when heated above 840°C, so gentle heating from a Bunsen burner would not be sufficient.
  15. Mathemagical

    Chemistry: Post your doubts here!

    Since this is obviously a decomposition reaction, we can conclude that one mole of N2F4 decomposes into 2 moles of NF2. Therefore, only the N-N bond in the middle is broken, and not the N-F bonds. Option 1 is incorrect. Option 2 states that the enthalpy change of the reaction is +160kJ/mol...
  16. Mathemagical

    Chemistry: Post your doubts here!

    The melting points of SiO2 and CaCo3 are 1600°C and 825°C respectively. Such high temperatures cannot be achieved by using a Bunsen burner, and so both of them would not melt under a Bunsen flame.
  17. Mathemagical

    Chemistry: Post your doubts here!

    The answer is A, sodium chloride. Upon addition of dilute aqueous ammonia, the precipitate dissolves, so chloride ions are present.
  18. Mathemagical

    Chemistry: Post your doubts here!

    The equilibrium constant is only affected by temperature, and not by anything else.
  19. Mathemagical

    Chemistry: Post your doubts here!

    The first reaction in which the intermediate is formed is nucleophilic substitution. For nucleophilic substitution, either sodium cyanide or potassium cyanide in ethanol can be used. Hydrogen cyanide is used in nucleophilic addition reactions, for example with aldehydes or ketones.
  20. Mathemagical

    Chemistry: Post your doubts here!

    The keyword in Question 22 is "followed by". Take Option B, for example. After polymerising it, the alkene becomes saturated and therefore cannot undergo a reaction with cold, dilute KMnO4. Similarly, alkanes, which are also saturated, cannot undergo that reaction.
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