Question

One cup of fresh orange juice contains 124 mg of ascorbic acid (vitamin c, c6h8o6). given that one cup = 236.6 ml, calculate the molarity of vitamin c in organic juice.

Answer 1

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. i hope this helps :)

Answer 2

Answer : The molarity of vitamin c in organic juice is, $2.97\times 10^{-3}mole/L$

Solution : Given,

Mass of ascorbic acid (solute) = 124 mg = 0.124 g        $(1mg=0.001g)$

Volume of juice = 236.6 ml

Molar mass of ascorbic acid = 176.12 g/mole

Formula used :

$Molarity=\frac{\text{Moles of solute}\times 1000}{\text{Molar mass of solute}\times \text{volume of solution}}$

Now put all the given values in this formula, we get the molarity of vitamin c in organic juice.

$Molarity=\frac{0.124g\times 1000}{176.12g/mole\times 236.6ml}=2.97\times 10^{-3}mole/L$

Therefore, the molarity of vitamin c in organic juice is, $2.97\times 10^{-3}mole/L$