Question

One cup of fresh orange juice contains 118 mg of ascorbic acid (vitamin C, C6H8O6). Given that one cup = 225.2 mL calculate the molarity of vitamin C in organic juice.

Answer 1

Answer;

The molarity of vitamin C will be; 0.002977 M or 2.977× 10^-3 M

Solution;

0.2252 L = 1 cup

118 mg of ascorbic acid = 0.118 g

1 mole of ascorbic acid = 176 g

Thus; 0.118g C6H8O6 x (1 mol C6H8O6 / 176.0g C6H8O6) / 0.2252L = 2.977x10^-3M .

=0.002977 M or 2.977× 10^-3 M

Answer 2

The formula for calculating molarity is moles of solute divided by liters of solution, thus the unit of molarity is moles/liter (M/L). To calculate molarity find the number of moles of solute and the volume of solution in liter.
To solve the problem above, convert 118 mg of vitamin c to mole. To do this first find the molar mass of vit c from its structural formula given above:
molar mass of vit c = (12*6)+ (1*8)+ (16*6) = 176.
moles of vit c = 118mg C6H8O6 * (1 mol of C6H8O6/176mg of C6H8O6)
Mole of vit c = 0.67moles
convert 225.2ml to liter = 225.2/1000 = 0.2252.
molarity = 0.67/.2252 = 2.9M.