RESULT:
BRAND A
Mean volume:26.55 cm3
BRAND B
Mean volume:23.35 cm3
CALCULATION:
CH3COOH + NaOH → CH3COONa + H2O
BRAND A
No. of mole of NaOH used: (26.55 ÷ 1000) × 0.1=0.002655
No. of mole of NaOH used : No. of mole of CH3COOH used in titration
=1:1
No. of mole of CH3COOH used in titration = 0.002655
mass of CH3COOH per cm3 in a bottle is:
0.002655 × (12 × 2 + 1 × 4 + 16 × 2) × 10 ÷ 25 = 0.06372 g
Cost per mass of vinegar is:
3.6 ÷ (0.06372 × 250)
=$0.2259887 per g
BRAND B
No. of mole of NaOH used: (23.35 ÷ 1000) × 0.1=0.002335
No. of mole of NaOH used : No. of mole of CH3COOH used in titration
=1:1
No. of mole of CH3COOH used in titration = 0.002335
Mass of CH3COOH per cm3 in a bottle is:
0.002335 × (12 × 2 + 1 × 4 + 16 × 2) × 10 ÷ 25 = 0.05604 g
Cost per mass of vinegar is:
7.6 ÷ (0.05604 × 473)
=$0.286717581 per g
CONCLUSION
Narcissus-Rice Vinegar is much cheaper than Heinz-distilled white vinegar.
DISSCUSION
- The solution used to rinse the burette, pipette and volumetric flask depend on which solution is going to be poured into. The 0.1M NaOH should be used to rinse the burette. Deionized water is used to rinse the volumetric flask. When vinegar is transferred to the volumetric flask, the vinegar should be used to rinse the pipette. While diluted vinegar is transferred, the diluted vinegar should be used to rinse the pipette.
- Phenolphthalein, instead of other indicator such as methyl orange, should be used because phenolphthalein changes its color sharply at about pH7.
- It is found that 3 drops, instead of 1 drop, of phenolphthalein should be added as it gives a sharper color change.
- The diluted vinegar should first be poured into a small beaker before pipetting as it avoid the pollution of the whole diluted vinegar.