Chemistry

Find the pH of 1.0E-8 M H2S04 (H2SO4 <==> 2H^+ + SO4^2-)

I have got answer to be 7.70, can you confirm the answer for me please?
If it is not good, i'll be very grateful if you could leave some guides.

  1. 👍 0
  2. 👎 0
  3. 👁 204
asked by Matt
  1. It isn't right and your gut should tell you that. How can you have an acid solution with a pH greater than 7. Remember 7 is neutral so a pH of 7.70 means your acid solution is basic and that can't be. Where are you in chemistry? If it is not beginning chemistry there are three things to do here. First, the ionization of H2SO4 occurs in two steps. The first step is 100% dissociation in which
    H2SO4 ==> H^+ + HSO4^-.
    Next, the HSO4^- dissociates but it is not 100%; i.e., the Ka is about 0.012. You should confirm that number from your Ka tables in your text.
    You can take both of these into account as follows:
    ........H2SO4 ==> H^+ + HSO4^-
    I.......1E-8......0......0
    C......-1E-8.....1E-8...1E-8
    E........0.......1E-8...1E-8

    Then k2 kicks in.
    ...........HSO4^- ==> H^+ + SO4^2-
    I.........1E-8........1E08....0
    C..........-x.........x.......x
    E........1E-8 - x....1E-8+x...x

    k2 = 0.012 = (H^+)(SO4^2-)/(HSO4^-)
    0.012 = (1E-8+x)(x)/(1E-8-x)
    If you are in beginning chemistry your prof PROBABLY doesn't expect you to do this so I've gone ahead and solved the quadratic above and obtained x = 1e-8 and that added to 1E-8 = 2E-8M and that is exactly the same number you would obtain if you worked the problem straight. Starting with 1E-8M H2SO4 you get 2H^+/mol H2SO4 and that gives you 2E-8M. That takes care of the first two reasons and my guess is the prof expects you to simply multiply 2*1E-8 = 2E-8M.

    The next step is to realize that at this low concentration you can't ignore the H^+ that comes from the ionization of water. So this is what you do.
    ...........H2O ==> H^+ + OH^-
    I.........liquid...0......0
    C.........liquid...x......x
    E.........liquid...x......x
    -----------------------------
    then add the 2E-8M to this to give you
    add...............2E-8..........
    new E............2E-8+x.....x

    Kw H2O = 1E-14 = (H^+)(OH^-)
    1E-14 = (2E-14+x)(x)
    Solve that quadratic for x, add x to 2E-8 and convert that H^+ to pH. I ran through it very fast and came up with 6.95 and we know it should be less than 7. Hope this helps.

    1. 👍 0
    2. 👎 0
    posted by DrBob222

Respond to this Question

First Name

Your Response

Similar Questions

  1. chem

    Sulfuric acid reacts with sodium hydroxide according to this equation: H2S04 + 2 NaOH Na2(SO4) + 2 H2O A 10.00 mL sample of the H2SO4 solution required 13.71 mL of 0.309 M NaOH for neutralization. Calculate the molarity of the

    asked by Liang9506 on November 21, 2012
  2. Chemistry

    H2SO4 solution containing 200.1g of H2S04 in 0.3500l of solution at 20 degree celcius has a density of 1.3294g/ml. find a,mass percent of H2SO4 b,molarity c,molality

    asked by GETU on December 17, 2018
  3. chemistry

    Aluminum reacts with sulfuric acid, which is the acid in car batteries. If 20.0 grams of Al is placed into a solution contain 115 gram of H2SO4, how many grams of hydrogen ga could be be produced? 2Al + 3H2SO4 ---> Al(SO4)3 + 3H2

    asked by mike on May 15, 2007
  4. chemistry

    Al(s) + H2SO4(aq)-> Al2(SO4)3(aq) + H2(g) Consider the unbalanced equation above. What volume of 0.490 M H2SO4 is needed to react with excess aluminum to produce 1.60 g of Al2(SO4)3? Use a molar mass with at least as many

    asked by jade on March 12, 2012
  5. Chemistry pls help

    I have a chemistry question Please advise how do I prepare 1L of 75% H2SO4 from concentrated H2SO4 (98% of density 1.84g/ml)? Do you have an equation which i can use? Someone gave me the following equation but I do not understand

    asked by tricia on December 3, 2008
  6. Chemistry Stiochiometry

    PLEASE HELP how many grams of AL2(SO4)3 can be made by reacting 50ml 2.8M H2SO4 with 7.4g of AL(OH)3? 3 H2SO4 + 2 Al (OH)3 ----> 6 H20 + AL2(SO4)3

    asked by Yasmine on June 4, 2018
  7. Chemistry

    What is the minimum amount of 6.6 M H2SO4 necessary to produce 22.6 g of H2 (g) according to the following reaction? 2Al(s)+3H2SO4(aq)→Al2(SO4)3(aq)+3H2(g) I need to find the volume of the H2SO4 Work: 22.6g H2 /2.008g H2 = 11.3

    asked by Finn on October 3, 2015
  8. Chemistry

    There's reaction involving gas: Fe + H2SO4 -> Fe2(SO4)3 + H2O + SO2 How Fe2(SO4)3 is occur? I know the "2" comes from the ion of SO4, but I don't know where the "3" comes up. Is the Fe2(SO4)3 comes up from half-reaction method? Is

    asked by Jeremy on March 19, 2015
  9. Chemistry

    What is the net ionic equation when H2SO4 is neutralized by NaOH in aqueous solution? Write the molecular equation. H2SO4 + 2NaOH ==> Na2SO4 + 2H2O Convert to ions. 2H^+ + SO4^= + 2Na^+ + 2 OH^- ==> 2Na^+ + SO4^= + 2H2O Now cancel

    asked by Bob on February 17, 2007
  10. Chemistry

    Calculate the volume (in mL) of 9.0M H2SO4 that you would need to convert 0.070 moles of KAl(OH)4 to K2SO4 and Al2(SO4)3 according to the following equation: 2 KAl(OH)4 + 4 H2SO4->K2SO4 + Al2(SO4)3 + 8 H2O

    asked by Cynthia on February 29, 2012

More Similar Questions