What was causing the very weird problem?

[apchemstudent]

Very weird problem here...

Problem solved... nm thanks for your help though...

 

[so-crates]

0.035 L * 3 M of H2SO4 = 0.105 mols of H2SO4
H2SO4 -> 2 H+ + SO42-

there's your first problem. Polyprotic acids don't disassociate all at once. The correct reaction would be
$$H_2SO_4 \longrightarrow H^+ + HSO_4^-\ \ \ K_a = high$$
$$HSO_4^- \longrightarrow H^+ + SO_4^{2-}\ \ \ K_a = a\ lot\ less$$

 

[apchemstudent]

there's your first problem. Polyprotic acids don't disassociate all at once. The correct reaction would be
$$H_2SO_4 \longrightarrow H^+ + HSO_4^-\ \ \ K_a = high$$
$$HSO_4^- \longrightarrow H^+ + SO_4^{2-}\ \ \ K_a = a\ lot\ less$$

Ya, i think my teacher wants to pretend it dissociates completely. However though, that still won't solve my problem. If we pretend only 1 H+ dissociates we have 0.105 moles of H+

(.105 - .075)/3 does not equal .105/4

 

[so-crates]

Could you state the exact wording of the problem? What you wrote is rather confusing.

 

[chem_tr]

Yes, apchemstudent, please write the exact wording and we will discuss it. It is good that you've made much effort to solve it, and maybe we'll see a little point you may have forgotten.

 

[apchemstudent]

figured out the mistake...