In: Chemistry
Molarity of standard NaOH solution: x/1 H 2/3 Unknown + 2/3 NaOH -> 2/3 H2O +Na 2/3 Acetate
Vinegar: | Titration 1 | Titration 2 | Tirtration 3 |
Initial V of Acid | .01 mL | 5.56 mL | 11.32 mL |
Final V of Acid | 5.56 mL | 10.71 mL | 16.02 mL |
Inital V of Base | .01 mL | 27.12 mL | 3.01 mL |
Final V of Base | 22.23 mL | 44.71 mL | 24.90 mL |
Unknown Acid code and number of reactive hydrogens: H+3
Unknown Acid | Titration 1 | Titration 2 (Error) | Titration 3 | Titration 4 |
Mass of Acid | .1024 g | .1028g | .1021g | .1023g |
Initial V of Base | 24.90 mL | 37.80 mL | 45.5 mL | 9.24 mL |
Final V of Base | 37.80 mL | 45.5 mL | 9.24 mL | 17.80 mL |
10. Find the moles of base (NaOH) for each of your unknown acid titrations.
11. Find the balanced equation using the number of reactive hydrogens (call an acid with one reactive hydrogen HA, one with two reactive hydrogens H2A, and so on).
12. Find the moles of unknown acid for each of your three unknown acid solutions.
13. Use the mass of unknown acid and the moles of unknown acid to find the formula mass of your unknown acid for each of your three unknown acid titrations.
Unknown Acid |
Titration 1 |
Titration 2 (Error) |
Titration 3 |
Titration 4 |
1. Mass of Acid |
.1024 g |
.1028g |
.1021g |
.1023g |
2. Initial V of Base |
24.90 mL |
37.80 mL |
45.5 mL |
9.24 mL |
3.Final V of Base |
37.80 mL |
45.5 mL |
59.24 mL |
17.80 mL |
4 . VNaOH used in titration, mL (line 3 – lin2) |
12.90 |
7.70 error |
13.74 |
8.56 error |
5. n, mol of NaOH used |
…… |
…. |
…. |
….. |
6. moles of unknown acid Line 5 divided by 3 |
….. |
…… |
… |
….. |
7. molar mass of H3A (line 1 / line 6) |
…. |
Not used |
…… |
Not used |
10.
For line 5:
n, mol of NaOH used = VNaOH (from line 4) x CNaOH
(I don’t have here the value of NaOH)
11.
H3A + 3 NaOH = Na3A + 3 H2O
12.
“the moles of unknown acid for each of your three unknown acid solutions” are calculated as
Line 5 divided by 3
(the molar ratio H3A / NaOH is 1:3)
13.
If titration 2 is an error. Titration 4 is also an error.
Use only titrations 1 and 3 to calculate the molar mass. Calculate the average value.