Question

Based off info below please answer blank boxes. Thanks!

Application Questions:

12. Before using a solution of NaOH as a standard for a titration, its precise concentration must be determined by titration with a standard acid. This is because solid NaOH absorbs water from the atmosphere, so its solid form is difficult to keep free of contaminated H₂O. A common acid used for standardization is the acid-salt, potassium hydrogen phthalate (KHP), KHC₈H₄O₄. Another way is to use a standardized solution of sulfuric acid:

H₂SO₄(aq)   +   2NaOH(aq)       ®      2H₂O(l)   +   Na₂SO₄(aq)

If 16.27 mL of 0.1125 M H₂SO₄ is required to titrate a 20.00 mL solution of NaOH, what is the molar concentration of the NaOH solution? Show your work.

    
  

13. A student wanted to know the mass of vitamin C (ascorbic acid) in a vitamin C tablet. She dissolved the tablet in water and then titrated with 0.200 M NaOH. The balanced equation for the acid-base neutralization reaction is:

HC₆H₇O₆(aq)   +   NaOH(aq)       ®      H₂O(l)   +   NaC₆H₇O₆(aq)

If 24.41 mL of NaOH was required to reach the endpoint, how many moles of ascorbic acid are in the tablet?You don’t need to show your work here.

  
  

What is the mass of ascorbic acid in the tablet?(MM = 176.12 g/mol)

  
  

Given that the student measured the mass of the vitamin C tablet as 4.601 g, calculate the percent-by-mass of ascorbic acid in the tablet.

  

  
  

Answer 1

The reactiion is

2NaOH+ H2SO4----> Na2SO4+ 2H2O

It suggersts that two moles of NaOH is requuried to react with 1 mole sof H2SO4.

Moles of H2SO4= Molairty * Volume of H2SO4= (16.27/1000)*0.1125 =0.00183 moles

Hence,. moles of NaOH reqiored = 0.00183*2 = 0.003661

From moles= Molarity* Volume

0.003661 =Molarity* (20/1000)

Molairty =0.003661*1000/20=1.833305M

b)

as per the reaction, one mole of NaOH is required to neutralize 1 moles of Ascorbic acid

Moalirt of NaOH =0.2M

Volume consumed =24.41ml=24.41/1000 liters =0.02441liters

Moles of NaoH =0.2*0.02441=0.004882 gmoles

Hence, moles of ascorbic acid in the tablet = 0.004882 gmoles

Molecular weight of Ascorbic acid ( HC6H7O6) =1+ 6*12+1*7+6*16= 176

Moles = mass/ molecular weight=

Mass of ascorbic acid =Moles* Molecular weight =0.004882 *176 =0.8592 gms

Mas of the vitamin C = 4.601 gms

Mass % of ascorbic acid = (mas of ascorbic acid/ mass of vitamin)*100 =(0.8592/4.601)*100=18.67%