5. How would the following errors affect the calculation of mg of citric acid pr

Question

5. How would the following errors affect the calculation of mg of citric acid present per mL of juice? Will it make the values too large or too small or no effect? Explain your answers. a. Overtitrating the end point. b. Stop titrating at the first sign of pink in the solution. c. Recording that 20.0 mL of juice was titrated, when actually only 10 mL of juice was present. d. The Molarity of NaOH was recorded as 0.180 M NaOH, instead of the actual molarity of 0.109 M NaOH. 6. If the juice to be titrated was yellow, the end point color would change from the pink to more of a peach (pink of the indicator at the end point + yellow solution = peach color). Would you be able to titrate purple grape juice by this technique? 7. In the introduction, we stated that other acids are present in fruit juices, but we assumed that the only acid that we were titrating was citric acid. Does this assumption make our results of mg of citric acid present per mL of juice high or low? Explain.

Explanation / Answer

a. Overtitrating the end point- moles of base calculated will be higher than actual value.therefore it gives higher citric acid amount than actual amount.

b. Stop titrating at the first sign of pink in the solution - excact endpoint is taken.therfore no effect on the final value.

c. Recording that 20.0 mL of juice was titrated, when actually only 10 mL of juice was present.- finally n= cv is used to calculate the concentration of citric acid.so here volume used for the calculation is higher than actual value.so according to the above equation it gives smaller concentraion value than the actual value.

d. The Molarity of NaOH was recorded as 0.180 M NaOH, instead of the actual molarity of 0.109 M NaOH - no of moles of NaOH is higher than actual value.therfore citric acid moles also will be higher.n=cv so conentration will be higher than actual value of citric acid.

7. In the introduction, we stated that other acids are present in fruit juices, but we assumed that the only acid that we were titrating was citric acid. Does this assumption make our results of mg of citric acid present per mL of juice high or low - we assume all the NaOH moles were used for citric acid.therfore citric acid moles also will be higher than actual value.so concentration of citric acid is higher than actual value.

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