## 6D. 7

KNguyen_1I
Posts: 101
Joined: Sat Aug 17, 2019 12:16 am

### 6D. 7

Find the initial concentration of the weak acid or base in
each of the following aqueous solutions: (a) a solution of HClO with
pH 4.60; (b) a solution of hydrazine, NH2NH2, with pH 10.20.

Just to clarify, wouldn't I need Ka and Kb to solve these problems? And so if we get this question on a test, we'd be given them right?

Maia_Jackson_2C
Posts: 101
Joined: Fri Aug 30, 2019 12:17 am

### Re: 6D. 7

Yeah I'm pretty sure you would need to be given Ka and Kb, because using the pH you can find the concentrations of H3O+ and OH-, but not the constants. I think they would give them to us on the test.

peteryim
Posts: 54
Joined: Sat Sep 07, 2019 12:17 am

### Re: 6D. 7

I'm not really sure what this question is asking, but I don't think you need Ka or Kb. It looks like the questions just wants you to convert pH into concentration of [H3O+].

Aman Sankineni 2L
Posts: 103
Joined: Fri Aug 30, 2019 12:17 am

### Re: 6D. 7

To start this problem, you would need to convert the pH into molarity by using 10^-4.60. Then, set up an ICE table with the molarity found as the H3O+ equilibrium concentration. Set the initial condition of HClO to x then subtract the molarity found from that, which will be the final equilibrium of HClO. You can then set up an equilibrium expression, set the equilibrium expression equal to the Ka value of HClO, and solve for x.

Repeat for part b.