## Photon336 one year ago Discussion/Questions acids and bases

1. Photon336

370/371/372

2. Photon336

373

3. Photon336

@Rushwr @sweetburger @Woodward

4. Rushwr

370. I will go with C Beacuse Strong acids don't form conjugated acids. They form conjugate base . The conjugate base for this is NO3^-1

5. Rushwr

371. I'll go with A $Ka = \frac{ [H ]^{2} [S ^{2-}]}{ [H _{2}S] }$

6. Rushwr

this is the Ka equation for the overall reaction.

7. Photon336

i think it gives the Ka for the H2S

8. Photon336

Ka1 = 1x10^-7 ka just compares exponents so it would be i think 7

9. Rushwr

To find Ka we have o multiply Ka1 and Ka2 and get the pKa

10. Photon336

they say that because the second kA is so small you can just ignore it.

11. Photon336

but wait is that what you are supposed to do? i forgot that

12. Photon336

i'm just curious

13. Rushwr

IDK that but what I know is what I did . for 372 i'll go with D

14. Rushwr

wait it must be that then! What is the answer given for that is it 7?

15. Rushwr

373. it would be thymol blue !

16. Rushwr

Since it is a weak acid strong base titration the anionic hdrolysis occur making the medium basic at its equivalence point. Hence the pH increases !

17. Photon336

going to leave this open coming back later.

18. Rushwr

oki doki

19. anonymous

Well I thought 371 was supposed to be kind of like a trick question but then again I should probably review my acid base things. I thought we would say pKa of $$H_2S$$ would be 7 and that the other value would be the value of the pKa of $$HS^-$$.

20. anonymous

372 seems fun one cause you really get to compare pKas of all these conjugate acids and bases. I guess the question is, which one of these answer choices is most basic?

21. Photon336

@Woodward the solution said that because the second pKa was so small you could just ignore it.

22. Photon336

$K _{3}PO _{4} ---> PO _{4} +3K ^{+}$ |dw:1439180017859:dw| $PO _{4} + H2O --> HPO4 + OH ^{-}$ not sure

23. Photon336

372 not sure, think it would probably be the one that is most basic.

24. Rushwr

So the K+ ions are present in the solution right so won't it form KOH by combining with OH- ions. ?????? I am bad when it comes to inorganic. But what was the answer given? @Photon336

25. Photon336

yeah well.. let me see for 372. the answer is C.

26. Photon336

|dw:1439255147994:dw| |dw:1439255180440:dw| CH3CH2OH wouldn't raise the concentration of hydroxide ions, because it can't deprotinate water, don't think it's kb is that high. For basic compounds Kb > ka producing OH- ions the compound would have to act a as a base. and have a pKa that's higher than that of water, in -order to deprotinate it.

27. Photon336

@Rushwr it's poorly written but the PO4 ion produces the most OH- ion concentration. in this case i think that the PO4 ion is acting as a base to deprotinate water and produce OH ions. it's pKa must be higher than water i think in order to deprotinate the water. this would imply that it's not really stable in solution.