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  1. H

    A level Biology: Post your doubts here!

    thank you so much but i am a little confused. how can we call a bond stable and high energy at the same time?
  2. H

    A level Biology: Post your doubts here!

    could somebody please tell me why amp hydrolysis releases less energy than hyrolysis of atp or adp, with reference to bonds?
  3. H

    Chemistry: Post your doubts here!

    Thank you so much!!
  4. H

    Chemistry: Post your doubts here!

    Q3)b) i) Why does Br2 not react with the double bond? ii)why does ethyol chloride not react with N in the ring ?
  5. H

    Chemistry: Post your doubts here!

    why does br2 not react with the double bond?
  6. H

    Chemistry: Post your doubts here!

    How many stereoisomers does piperic acid have? I mean the answer is 4 but i actually drew 8 of them and they are all different in terms of spatial arrangement. I hope you understand the spatial crisis here. I would be grateful if somebody could explain it to me.
  7. H

    Chemistry: Post your doubts here!

    salaam! could somebody please tell me that when we are drawing graphs of temperature against time or any value like volume of a solution , how are we supposed to draw the line through the points? i mean are we supposed to start from the initial temperature or should we draw the line such that...
  8. H

    Chemistry: Post your doubts here!

    Can somebody please explain me how can the two structures be optical isomers. I mean shouldn't the carboxylic grip on the upper side in the second structure face the opposite side to the left I mean. The same applies for the OH in the carboxylic group on the mower side in the second structure.
  9. H

    Physics: Post your doubts here!

    As the lift is accelerating down, there is a resultant force acting on the man and the lift (2nd law of newton) F=ma the resultant force F is equal to weight of the man minus the tension in the cable of the lift so technically the force exerted by the man us less that its weight.
  10. H

    Physics: Post your doubts here!

    The current in the horizontal resistors is 8,3 and 1 respectively and across the vertical resistors is 5, 2 and 1 respectively. By this calculate voltage across each resistor and the total potential difference across the 1st horizonal resistor and 1 vertical resistor gives us the voltage across...
  11. H

    Physics: Post your doubts here!

    Thank you but why do we use 2.7?
  12. H

    Physics: Post your doubts here!

    If that's the answer why would they ask the question It means to draw a single line . It need not to be horizontal. A curved path is a line too.
  13. H

    Physics: Post your doubts here!

    For the first question, the wave that will be drawn on the graph is going to be a simple wave like you see in the textbook with crests and troughs . Stationary waves only move up and down. There is no propagation of wave. At t =0 , the stationary wave is in the middle . It takes 20 ms for it to...
  14. H

    Physics: Post your doubts here!

    http://pastpapers.papacambridge.com/view.php?id=Cambridge%20International%20Examinations%20%28CIE%29/AS%20and%20A%20Level/Physics%20%289702%29/2017%20Nov/9702_w17_qp_22.pdf could somebody please explain me Q3)d) Where is the force 2.7 on the spring acting and how the spring can not have...
  15. H

    Float like a butterfly, sting like a bee. His hands cant hit what his eyes can't see

    Float like a butterfly, sting like a bee. His hands cant hit what his eyes can't see
    • hamadh
    • Profile post
  16. H

    Chemistry: Post your doubts here!

    a big big big thanks to you from my side. but isn't it a bit misleading to write -781.4 per mole. They could have just written enthalpy change = 781.4 . i hope i am not annoying you. this per mole thing is what is causing me the whole confusion anastasia grey113
  17. H

    Chemistry: Post your doubts here!

    Thank you so much for the reply. I wanted to ask why don't we multiply enthalpy change for sulfurtrioxide with 2 .
  18. H

    Chemistry: Post your doubts here!

    Sulfur can be oxidised in two ways. S(s) + O2(g) → SO2(g) ∆H o = –296.5 kJ mol–1 2S(s) + 3O2(g) → 2SO3(g) ∆H o = –791.4 kJ mol–1 Sulfur trioxide can be made from sulfur dioxide and oxygen. 2SO2(g) + O2(g) → 2SO3(g) What is the standard enthalpy change for this reaction? A...
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