Marshmallow Packet pH

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halle young 4A
Posts: 68
Joined: Thu Jul 11, 2019 12:16 am

Marshmallow Packet pH

Postby halle young 4A » Wed Dec 04, 2019 3:57 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 last with water up to the 1L mark, what is the pH of the resulting solution?

how do we find pH given these values? did we go over this in class or is there a section in the book i might find helpful?

Esha Chawla 2E
Posts: 108
Joined: Thu Jul 25, 2019 12:17 am

Re: Marshmallow Packet pH

Postby Esha Chawla 2E » Wed Dec 04, 2019 4:55 pm

halle young 4A wrote: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 last with water up to the 1L mark, what is the pH of the resulting solution?

how do we find pH given these values? did we go over this in class or is there a section in the book i might find helpful?


We went over this today in class. First, convert the miligrams of HCl into moles - this is also the number of moles of H+. Similarly, convert the miligrams of CaO into moles - this is the number of moles of OH-. Subtract the two from each other - in this case, there is more H+ than OH-. Take the -log of this value.

mayarivers3I
Posts: 52
Joined: Wed Sep 18, 2019 12:18 am

Re: Marshmallow Packet pH

Postby mayarivers3I » Sat Dec 07, 2019 12:57 pm

I don't see the answer key for the marshmallow practice problems so can someone tell me if the answer to 34 is a pH of 2.1?

Simon Dionson 4I
Posts: 107
Joined: Sat Sep 14, 2019 12:17 am

Re: Marshmallow Packet pH

Postby Simon Dionson 4I » Sat Dec 07, 2019 2:03 pm

mayarivers3I wrote:I don't see the answer key for the marshmallow practice problems so can someone tell me if the answer to 34 is a pH of 2.1?


I'm not sure if it's 2.1 or 2.3. CaO + H2O --> Ca(OH)2. There are 2 hydroxides produced for every 1 CaO. If you double the moles of OH-, the answer comes out to 2.276 vs 2.1 if you just had 1 mol OH- per 1 CaO


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