Posted by Chem on Monday, August 10, 2009 at 8:08pm.
1) How many drops of 12M HCl would you add to 1.00 L of 0.100 M HC2H3O2 to make [C2H3O2-] = 1.0 x 10^-4 M? Assume that 1 drop = 0.050 mL and that the volume of the solution remains 1.00 L after the 12 M HCl is diluted. [Hint: What must be the [H3O+] in the solution?]
2. What mass of NaC2H3O2 should be added to 1.00 L of 0.100 M HC2H3O2 to produce a solution with pH = 5.00? Assume that the volume reamins 1.00 L.
Chemistry - DrBob222, Monday, August 10, 2009 at 10:46pm
I accidentally deleted my response. Let me know if you didn't get it and I will repost.
Chemistry - Chem, Tuesday, August 11, 2009 at 7:44am
Can you repost #1 please. Thanks.
Chemistry - DrBob222, Tuesday, August 11, 2009 at 12:11pm
Let't call acetic acid, HC2H3O2, HAc.
HAc ==> H^+ + Ac^-
Ka = (H^+)(Ac^-)/(HAc)
Ka is about 1.8 x 10^-5 but you need to verify that from your text.
You know Ka, (Ac^-) is 1 x 10^-4 from the problem and (HAc) is 0.1 from the problem. Calculate (H+) that is needed.
Since you have a liter of solution, the moles H^+ (moles/L) will be the same as the molarity.
Now determine how much of the 12 M HCl must be added to make the H^+ from above.
12 M x volume = moles H^+.
Then knowing that each drop is 0.05 mL, convert volume to drops.
I played around with some numbers in my head and came up with approximately 6 mL and 120 drops BUT check my work. I just estimated here and there. You MUST do it yourself to confirm.
The second problem is one to solve using the Henderson-Hasselbalch equation.
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