## Question 12.61 (Sixth Edition)

Steve Magana 2I
Posts: 61
Joined: Fri Sep 28, 2018 12:24 am

### Question 12.61 (Sixth Edition)

Question: 12.61 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.

I'm having trouble starting this question, can someone help please? Thank you!

KatelinTanjuaquio 1L
Posts: 69
Joined: Fri Sep 28, 2018 12:16 am
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### Re: Question 12.61 (Sixth Edition)

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.

Jayasuriya Senthilvelan 4I
Posts: 31
Joined: Thu Jan 10, 2019 12:17 am

### Re: Question 12.61 (Sixth Edition)

Set up an ICE table, but this fill in the equilibrium concentration of H+ ions (do 10 ^ -pH). Write the reaction, and it should be evident that the concentration of H+ is the same as that of the equilibrium concentration of conjugate. Then, if we suppose that we start with some x amount of initial acid, then the equilibrium concentration of unreacted acid is x - i, where i the concentration of H+ ions (since the concentration of H+ ions at equilibrium is equal to the change). Then, plug in all your numbers in to equation for the Ka, and solve!

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