Question

A label from a container of orange juice is shown below:

(i). Calculate the moles of vitamin C in a 20mL “mouthful” of the orange juice. Check the structural formula in the image above.

(ii). Vitamin C reacts with water to form the ascorbate ion according to the following equation:

C6H8O6(s) + H2O(l) C6H7O6-(aq) + H3O+(aq)

Identify the two bases in this equation.

Answer 1

(i). Assumptions: The content of vitamin C in orange juice is 50 mg per 100 g of product; 100 ml of orange juice weights 100 g.

Proportion:

100 ml – 50 mg

20 ml – x mg

x – 10 mg – content of vitamin C in 20 ml of orange juice

M(ascorbic acid) = 176.12 g/mol

n=m/M

n(ascorbic acid) = 0.01 g / (176.12 g/mol) = 0.000056 mol = 5.6×10^-5 mol

Answer: 5.6×10^-5 mol

(ii). The two bases in this equation are ascorbate C₆H₇O₆^- and water H₂O