Posted by jemima on Tuesday, December 11, 2012 at 12:14am.
mols NH3 = M x L = ?
mols NH4Cl = M x L = ?
pH = pKa + log(b/a)
9.5-9.25 + log (10/0./2x)
Solve for x and convert to mL.
thank you that definitely helps. i just have one question, line 5:
9.5-9.25 + log (10/0./2x) is that supposed to read
9.5-9.25 + log (10/0.1/2x)? just a bit confused.
thank you that definitely helps. i just have one question, line 5:
9.5-9.25 + log (10/0./2x) is that supposed to read
9.5-9.25 + log (10/0.1/2x)? just a bit confused., and also why is it divided by 2x? i have an exam for this on friday morning.
Sorry about that. I made several typos.
First mols = M x L (which is right BUT I used millimoles in the equation that follows).
100 mL x 0.100M = 10 millimols NH3.
x mL x 0.2M = 0.2x millimols NH4^+. Using millimoles, it should read
pH = pKa + log(base/acid)
9.5 = 9.25 + log(10/0.2x)
1.778 = 10/0.2x
0.3557x = 10
x = 10/0.3557 = 28.1 mL. Thank you for bringing this to my attention. Usually I check these fairly closely; I was in a hurry to leave today and didn't. I hope this clears things for you.
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