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  1. sergey_le

    Common ion in solution

    my approach is wrong or the one in the lasts year lab report?
  2. sergey_le

    Common ion in solution

    Summary:: finding concetrations [Thread moved from the technical forums] i did a lab experiment and i'm a little confused about what i should do. i got a solution of CaCl(2) 1.5 gr and Ca(OH)2 5gr in 100ml that i prepared 2 weeks ahead . after filttering the solution i got a saturated...
  3. sergey_le

    Chemical kinetics lab question

    last week i did a chemistry lab. i mixed NaOH 0.03M with equal part of methyl violet and mesured aborbance in a spectrophotometer. then i did the same thing with a 0.05M and methyl violet i did today the graphs and got the k' =-0.1647 for the first solution and k'=-0.4022 for the second...
  4. sergey_le

    Calculations involving acids and bases

    i found the pka=4.8 so the ka is 1.58*10^-5. i guess the big issue i have is understanding what equation i should use. i attached what idid so far ,can you give it a look and tell me where i am wrong?
  5. sergey_le

    Calculations involving acids and bases

    Summary:: finding ml of two solutions by the final pH i have a NaOAc 0.1M and HOAc 0.1M , together the volume of the solutions is 20ml and the pH is 4. I need to find the volume of each solution. I've tried to solve it for hours with no successes. i found the H+ concentration (-log(h)=4 ), it...
  6. sergey_le

    The most likely structure from combinations of these atoms

    an element (we will call it X) got a cofiguration of 1##s^2##2##s^2##2##p^6##3##s^2##s##p^3## what molecule is moste likely to happend between this element and Mg? 1.MgX 2.##Mg_2##X 3.Mg##X_2## 4.##Mg_3## ##X_2## how do i do it?with lewis structure?just check what structure makes the most...
  7. sergey_le

    Prove that this function is nonnegative

    Thanks so much I finally realized
  8. sergey_le

    Prove that this function is nonnegative

    Yes I'm sorry. I don't know why I make such mistakes
  9. sergey_le

    Prove that this function is nonnegative

    why x=3/2+πk is not a solution?
  10. sergey_le

    Prove that this function is nonnegative

    Yes I know how to solve it x(1 + sin(x)) = 0 when x=0 or x=3/2+πk
  11. sergey_le

    Prove that this function is nonnegative

    You mean I have to show that there is no f' axis with x axis?
  12. sergey_le

    Prove that this function is nonnegative

    nothing special. Please direct me
  13. sergey_le

    Prove that this function is nonnegative

    I'm sorry I don't understand what you want to say
  14. sergey_le

    Prove that this function is nonnegative

    Also the derivative f'(x)≥0 I don't understand what you want me to do? How do I show that f'(x)>0 And no ≥
  15. sergey_le

    Prove that this function is nonnegative

    I can show that f(x)≥0 .
  16. sergey_le

    Prove that this function is nonnegative

    If I use contradiction, So I have to assume that f(a)≤0 , And I don't see a reason why that f(a)=0
  17. sergey_le

    Prove that this function is nonnegative

    That's exactly my problem. Don't see a reason that z> 0
  18. sergey_le

    Prove that this function is nonnegative

    Yes but I can't use it in this course. In my course it is Calculus 2
  19. sergey_le

    Prove that this function is nonnegative

    If that was the case then I had no problem . But because it is ≤ Then there is the possibility that f'(x)=0.
  20. sergey_le

    Prove that this function is nonnegative

    No That's what I intended to do. But my problem is with the one that can be x∈(0,δ) (when are δ>0) so that f'(x)=0 and then f(0)=f(x)=0 for ∀x∈(0,δ) And then what I have to prove is wrong. Do you understand my problem?
  21. sergey_le

    Prove that this function is nonnegative

    What I wanted to do was set f(x)=##x^2##/2 - xcosx+sinx And show that f(x)>0. f'(x)=x(1+sinx) First I wanted to prove that f(x)<0 in the interval (0,∞) 0≤1+sinx≤2 And thus for all x> 0 f'(x)≥0 and therefore f(x)≥f(0)=0 And it doesn't help me much because I need to f(x)>0
  22. sergey_le

    Let a_n be sequence so that a_n+1-a_n>-1 and |a_n|>2 for all n.

    Well thank you very much I will try to find a solution already. Thanks also for your patience
  23. sergey_le

    Let a_n be sequence so that a_n+1-a_n>-1 and |a_n|>2 for all n.

    I meant what you wrote here. If you don't understand what I wrote, tell me and I'll upload a photo of the inequality. Because I can't post it with the forum tools
  24. sergey_le

    Let a_n be sequence so that a_n+1-a_n>-1 and |a_n|>2 for all n.

    I'm sorry I didn't write the problem to the end. Yes I meant it #<## a_n+1##<##\frac a_n a_1 ## Prove that if for every n is Happening ## a_n+1##<##\frac a_n a_1 ## then a1<0
  25. sergey_le

    Let a_n be sequence so that a_n+1-a_n>-1 and |a_n|>2 for all n.

    hiii :smile: If you can help me with this problem I would be very happy
  26. sergey_le

    Let a_n be sequence so that a_n+1-a_n>-1 and |a_n|>2 for all n.

    Yes it is clear. Do you want me to re-post the question or understand what I'm asking?
  27. sergey_le

    Let a_n be sequence so that a_n+1-a_n>-1 and |a_n|>2 for all n.

    I tried to use https://www.physicsforums.com/help/latexhelp/ . But it didn't work, Maybe my question is clearer now?
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