pH of a solution

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Brian Tangsombatvisit 1C
Posts: 119
Joined: Sat Aug 17, 2019 12:15 am

pH of a solution

Postby Brian Tangsombatvisit 1C » Sat Dec 07, 2019 12:18 pm

Lyndon sees his crush and panics, accidentally dropping 382.7 mg of HCl and 147.1 mg CaO into a 1L flask. After filling that flask with water up to the 1L mark, what is the pH of the resulting solution?

Sophia Shaka 3L
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Joined: Wed Sep 18, 2019 12:20 am
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Re: pH of a solution

Postby Sophia Shaka 3L » Sat Dec 07, 2019 12:33 pm

This is a strong acid/strong base reaction, so you need to determine whether the resulting solution has an excess hydronium or hydroxide through dimensional analysis with the balanced equations in water. It turns out there is more hydronium and pH=-log[H+]= 2.28.

Midori Hupfeld 3D
Posts: 55
Joined: Fri Aug 30, 2019 12:17 am

Re: pH of a solution

Postby Midori Hupfeld 3D » Sat Dec 07, 2019 12:35 pm

he most important part of this problem is remembering that CaO, a strong base, produces 2 moles of OH-. Convert these masses of HCl and CaO into moles of H+ and OH- respectively. It is basically like a limiting reactant problem, so whichever produces more H+ or OH- is in excess, and we want to find how much H+ or OH- is in excess. So, subtract the two values you got for the moles of OH- and H+ and divide that difference by the liters given, in this case it is 1 so doesn't matter but it will if the volume is anything other than 1. Then, you can plug this molarity into the pH (if H+ is in excess) to find pH, or pOH (if OH- is in excess) and subtract this from 14 to get pH.

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