2010/10/05

More questions...

A couple question...

---
I was just wondering about the oxidation number. example: PH3 P has 3+ and H has 1- so all you need to do is subract the two or do i have the method wrong. thanks
---

I'd start from the other direction on this, hydrogen is almost always oxidation number +1, so if there are 3 hydrogens at +1, and the molecule is neutral overall, then the phosphorus must be oxidation number -3.

---
I was doing one of the "Conceptual Exercise" problems and can't figure out how they came up with the answer that they did. It is 5.4 on page 175 part B. I came up with H^+ + OH^- yields H_2_0. It looks like that is the answer but then it has another equation for an answer as well. I know I am forgetting something simple but I can't figure out what it is and it's driving me nuts. Please help me out and thanks in advance.
---

These are a bunch of acid-base net ionic equations, so I'll address them all.

HCl(aq) + KOH(aq) --> H2O(l) + KCl(aq)
H+(aq) + Cl-(aq) + K+(aq) + OH-(aq) --> H2O(l) + K+(aq) + Cl-(aq)
Chloride ions and potassium ions don't change, so they are spectators and the net ionic equation is:
H+(aq) + OH-(aq) --> H2O(l)


H2SO4(aq) + Ba(OH)2(aq) --> 2 H2O(l) + BaSO4(s)
This one should look familiar...
2 H+(aq) + SO42-(aq) + Ba2+(aq) + 2 OH-(aq) --> 2 H2O(l) + BaSO4(s)
Since water is a molecule and barium sulfate is a precipitate, these both stay together in the full ionic equation, so the net ionic equation doesn't have any spectator ions here...
2 H+(aq) + SO42-(aq) + Ba2+(aq) + 2 OH-(aq) --> 2 H2O(l) + BaSO4(s)


CH3COOH(aq) + NaOH(aq) --> H2O(l) + NaCH3COO(aq)
You could also represent acetic acid and acetate ions as CH3CO2H/CH3CO2- or HC2H3O2/C2H3O2-. Acetic acid is a weak acid, so it should not be split up in the ionic equation:
CH3COOH(aq) + Na+(aq) + OH-(aq) --> H2O(l) + Na+(aq) + CH3COO-(aq)
The sodium ion is a spectator, so the net ionic is:
CH3COOH(aq) + OH-(aq) --> H2O(l) + CH3COO-(aq)

Other questions, let me know, I'll be checking email all evening. I'll also post answers first thing in the morning. Good luck...

No comments:

Post a Comment