[Nathaniel]

4.00 mol/L sulfuric acid, H2SO4(aq)

Here is my work
H2SO4 is one of those acids that is 100 percent ionized for the first H+ and less than 100% for the second one
H2SO4 --> H+ plus HSO4- 100%
H2SO4 --> H+ plus SO4- not 100%
H+ - 1.00 M for the first ionization
The second one is guided by K2
K2 = (H+)(HSO4-)/(HSO4-)
Plug in K2 as follows:
H+=1.00 + x
SO4 = x
HSO4 = 1.00 - x
I know I must solve for x

Can someone please help me reach the answer?

[Rabn]

first off you need to check your work for your equations in K2.  Start with the balanced chemical equation and build your I.C.E. chart(think about what your initial values are). fill in your K2 equilibrium equation.  THen rearrange your equation to solve for zero. I usually put the equation into my graphing calc and solve it for 0.

[Borek]

http://www.chembuddy.com/?left=pH-calculation&right=pH-polyprotic-simplified

Please don't post series of questions, if you want to post several - do it in one post. And posting four questions each time asking others to finish your calculations just doesn't sound right.

[AWK]

4.00 mol/L sulfuric acid, H2SO4(aq)

Here is my work
H2SO4 is one of those acids that is 100 percent ionized for the first H+ and less than 100% for the second one
H2SO4 --> H+ plus HSO4- 100%
H2SO4 --> H+ plus SO4- not 100%
H+ - 1.00 M for the first ionization
The second one is guided by K2
K2 = (H+)(HSO4-)/(HSO4-)
Plug in K2 as follows:
H+=1.00 + x
SO4 = x
HSO4 = 1.00 - x
I know I must solve for x

Can someone please help me reach the answer?

4.00 M or 1.00 M ?
Note, even for 1.00 M H2SO4 your calculations without ionic strength will give result different from a real pH value more than 0.5 pH unit.