6D. 7

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6D. 7

Postby KNguyen_1I » Sat Jan 18, 2020 4:25 pm

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?

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Re: 6D. 7

Postby Maia_Jackson_2C » Sat Jan 18, 2020 4:43 pm

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.

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Re: 6D. 7

Postby peteryim » Sat Jan 18, 2020 5:20 pm

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
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Joined: Fri Aug 30, 2019 12:17 am

Re: 6D. 7

Postby Aman Sankineni 2L » Sat Jan 18, 2020 5:33 pm

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.

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