Please help me about this chemical ploblem. A student weighs 2 vitamin C tablets

Question

Please help me about this chemical ploblem.

A student weighs 2 vitamin C tablets ( ascorbic acid, HC6H7O6 ) and finds the total mass to be 1.2004g.

She then dissolves them in water, and makes the solution up to a volume of 100.00 mL in a ftask. 20.00 mL of this solution is measured out with a pipet and then titrated with 0.005092M NaOH.

After addition of 22.58 mL of NaOH a pale pink end point is observed.

The balanced equation for te reaction is

HC6H7O6 + NaOH NaC6H7O6 + H2O

The molar mass of ascorbic acid( VitaminC) is 176.12 gmol. What is the percentage of Vitamin C in each tablet.

Explanation / Answer

from balanced equation :

moles of NaOH = moles of vitamic C

moles of NaOH = molarity x volume

= 0.005092 x 22.58 / 1000

= 1.15 x 10^-4

moles of vitamic C = 1.15 x 10^-4

mass =moles x molar mass

= 1.15 x 10^-4 x 176.12

= 0.0202 g

percent in vitmaic C = 0.0202 x 100 / 1.2004

= 1.69 %

for two tables % mass = 1.69 %

for each tablet = 0.843 %

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