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Everything posted by ChemSiddiqui

  1. I'd say if you have more wallpapers then contribute darkshade. Your ones are particularly good! and I don't see anyone else posting some wallpapers...not for a while anyway!
  2. Yes I did. Thank you again ! good day!
  3. O.alright Thank you very much hermantrude. I very much appreciate your help!
  4. Using the same reaction in equillibrium: CH3CO2H + C2H5OH <-------> CH3CO2C2H5 + H20 The reaction quotient will be 2/2 = 1 right (correct me if I am wrong). This is less than the kc of the reaction so the reaction should yeild less products and more reactants. But the mark scheme says the reaction sould yeild more products because the equillibrium amount is 0.1 + X and not 0.1 –X . So firtly clarify this point to me. Also say the RQ is less than kc i.e. the reaction will have the left shift, then sould the equillibrium amount be 0.5 + x in this case?
  5. O... I see you have to apply Le Chateleir's principal here then to see which direction the equillibrium shift and then determine the concentration. I understand completely now thank you very much zule. Good chatting with yeh. One more thing to hermanntrude. when you find the reaction quotient to determine the direction of shift of equillibrium, does the equillibrium amount of reactant remain the same all the time regardless of the direction of the shift?
  6. Ok. But what I wanted to ask was why it is 1 +X than 1-X amount after the equillibrium? although I understood what you had to say in your post but I am actually confused about the equillirium amounts? Sorry if it is annoying to you!
  7. I know darkshade its going good so far. Nice pics again mate. Here are some more from me:
  8. Thank you for the reply. But could you elaborate this point.
  9. Hi all! I was doing some past papers and I have some problem. The question was: Q. Alcohols and esters are important organic compounds which are widely used as solvents. Esters such as ethyl ethanoate can be formed by reacting carboxylic acids with alcohols. CH3CO2H + C2H5OH <------> CH3CO2C2H5 + H20 For this equilibrium, the value of Kc is 4.0 at 298K. A mixture containing 0.5 mol of ethanoic acid , 0.5 mol ethanol, 0.1 mol ethyl ethanoate and 0.1 mol water was set up and allowed to come to equilibrium at 298K. The final volume of the solution was V dm3. Calculate the amount, in moles, of each substance present at equilibrium. My try at the solution: CH3CO2H + C2H5OH <------> CH3CO2C2H5 + H20 Initial amounts: 0.5 0.5 0.1 0.1 Equilibrium amount: 0.5 – X 0.5 – X 0.1 – X 0.1 – X Concentrations at equilibrium: 0.5 – X 0.5 –X 0.1 –X 0.1 -X V V V V Kc = [CH3CO2C2H5] [H20] [CH3CO2H] [C2H5OH] Putting values in the formula makes: 4 = (0.1 –X)^2 (0.5 – X) ^2 4(0.5-X) = 0.1 –X X = 0.63Then evaluating each amount in equilibrium using x. But the mark scheme says that the value of x is 0.3. Also mark scheme says that amount in moles in equilibrium of water and ethyl ethanoate will be (1 + X) than (1-x)? That’s my question why is it? Any help will be appreciated!
  10. Ah.... Beautiful. I always fancy good DNA wallpapers. Thank you and also thanks to your brother for contributing.
  11. Very good darkshade, love the pics. And thank you for the link captainpanic!
  12. As you grow you change some habits but some are there unchanged. I love sleeping. I would slumber on my bed all day if i could help it. But, its how you want it really. I don't like to wake up too early, but at night I am very sleepy to even work but I force myself to work and waking up late at night has been worth it for me really. Remember its how you like to mould your habits, you dictate them and don't let the opposite happen. Live healthy!
  13. Its alright. I am following every single post in this thread and actually gaining a lot.
  14. Please post and contribute Chemistry wallpapers here in this thread:
  15. Bignose I figured it out later that I was doing alright. The solution was right but my substraction wrong (I had put my calculator in a diffrent mode). Thanks any way.
  16. My friend there is nothing else then to suggest you to work hard. Allah in Quran has stated: "What thy will seek is that thy will get". God has promised success if your intentions are pure and you are working exceedingly hard. Do both and leave it to God. You will become a physician I bet! Good Luck!
  17. Alright I was doing some statistics questions and I have a probelm. Here goes: The random variable Z is distributed such that Z find the probalility: P(lZl < 1.3) NB. < is actually less than equal to. My solution: P( -1.3< Z < 1.3) P(z<1.3) - [ 1- P( Z < 1.3)) After putting values from the table 0.9032 - (1-0.9032). 0.9032 -0.9068 = -0.0036 (probalility can't be negative so my answer is wrong, mark scheme is saying the answer is 0.8064) Thanks in advance.
  18. Please help me out on this. I need immediate answers if thats possible. I'll really appreciate any help. This query is from a friend who emailed me: The experiment was basically to find the percentage purity of three different brands of iron tablets. I did this through titration with potassium permanganate. I also had to do colorimetry with different concentrations of the iron solution and with ammonium thiocyanate (makes solution go red). I also had to do colorimetry changing the thiocyanate concentration and by keeping the iron concentration the same - this would allow me to find the order of reaction. However, i was unable to get these results and so i have had to make them up. I was wondering what the effect of changing the concentrations of thiocyanate and iron would have on the rate - would it double the rate of reaction. In this experiment iron is present as Fe3+ . i have made up the colorimetry results ( i have roughly made the rate double when the concentration of the chemicals are doubled) - making the overall rate of reaction second order. I appreciate your help. Thank you in advance!
  19. Thank you for your reply. But what you just said was the same thing I asked the reason for?
  20. Potassiun dichromate wouldn't work without any acidic medium. it needs acidity to work. Why does it do so like this I have no idea.. but you can search on the internet. I hope this is what you were looking for!
  21. I think YT is right, because when you look at oxidation states Cu forms then it is +2 which gives a blue ppt and Cu+1 which gives green. CU+2 being more stable. Also hydrogen peroxide is an oxidising agent so I doubt it would have any effect on CuSO4( there isn't any Cu+3 state)!
  22. And you did the right thing by making this sticky YT! good work! and to you too OP!
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