The triation of 50.00 mL of 0.025 00 M MES with 0.100 0 M NaOH. MES is a weak acid with pKa=6.27. Compute Ve, first. Show what happens at the four stages of the titration: Va = 0,2,5,10,10.1,11,12, and 12.2 mL.
I NEED HELP!!!!
Can you calculate volume to get to the equivalence point? Do that first.
a. First stage: at the beginning.
.........HA ==> H^+ + A^-
initial..0.025..0.....0
change...-x.....x.....x.
equil...0.025-x..x....x
Substitute into the Ka expression and solve for x, then convert to pH.
b. At the equivalence point you have the salt. The hydrolysis of the salt:
You will need to determine the concn of the salt. That will be (50*0.025/50+Ve)= ?
.........A^- + HOH ===> HA + OH^-
initial.. ?.............0.....0
change..-x..............x.....x
equil....?-x.............x....x
Kb for A^- = (Kw/Ka for MES) = (HA)(OH^-)/(A^-)
Substitute from the ICE chart and solve for x = (OH^-), then convert to pH.
c. Everything between beginning and the equivalence point.
mols MES = M x L
mols NaOH = M x L
Subtract which will leave an excess of MES PLUS the salt formed. I would use the Henderson-Hasselbalch equation which is pH = pKa + lopg (salt/acid)
d. Everything after the equivalence point.
mols EXCESS NaOH/total volume. This will be OH^-, convert to pOH, then to pH.
Post your work if you get stuck.
Sure! I can help you with that.
To calculate Ve, we need to determine the equivalence point of the titration. The equivalence point is the point at which the moles of acid (MES) are equal to the moles of base (NaOH) added. At this point, all of the MES will be neutralized.
The equation for the titration of MES (acid) with NaOH (base) is as follows:
MES + NaOH -> NaMES + H2O
To calculate Ve, you can use the following formula:
Ve = Va + Na / Nb * Va
Where,
Ve = equivalence point volume
Va = volume of acid (MES) added
Na = number of moles of acid present initially (50.00 mL * 0.025 00 M MES)
Nb = number of moles of base added
Now, let's calculate Ve at the given stages of the titration:
Stage 1: Va = 0 mL
Ve = 0 + (Na / Nb * 0) = 0 (no base added yet)
Stage 2: Va = 2 mL
Na = 50.00 mL * 0.025 00 M MES = 0.00125 mol
Nb = 0.100 0 M NaOH * 0.002 L = 0.0002 mol
Ve = 2 + (0.00125 / 0.0002 * 2) = 11 mL
Stage 3: Va = 5 mL
Na = 0.00125 mol (unchanged)
Nb = 0.100 0 M NaOH * 0.005 L = 0.0005 mol
Ve = 5 + (0.00125 / 0.0005 * 5) = 12.5 mL
Stage 4: Va = 10 mL
Na = 0.00125 mol (unchanged)
Nb = 0.100 0 M NaOH * 0.01 L = 0.001 mol
Ve = 10 + (0.00125 / 0.001 * 10) = 20 mL
Stage 5: Va = 10.1 mL
Na = 0.00125 mol (unchanged)
Nb = 0.100 0 M NaOH * 0.0101 L = 0.00101 mol
Ve = 10.1 + (0.00125 / 0.00101 * 10.1) = 21.35 mL
Stage 6: Va = 11 mL
Na = 0.00125 mol (unchanged)
Nb = 0.100 0 M NaOH * 0.011 L = 0.0011 mol
Ve = 11 + (0.00125 / 0.0011 * 11) = 20.227 mL
Stage 7: Va = 12 mL
Na = 0.00125 mol (unchanged)
Nb = 0.100 0 M NaOH * 0.012 L = 0.0012 mol
Ve = 12 + (0.00125 / 0.0012 * 12) = 12.5 mL
Stage 8: Va = 12.2 mL
Na = 0.00125 mol (unchanged)
Nb = 0.100 0 M NaOH * 0.0122 L = 0.00122 mol
Ve = 12.2 + (0.00125 / 0.00122 * 12.2) = 12.704 mL
I hope this helps you calculate Ve at each stage of the titration. Let me know if you have any further questions!