Question

111 Experiment 11 AN INSTRUMENTAL ANALYSIS OF POP FOR ITS PHOSPHORIC ACID CONTENT The Pre-Lab . A student performs an experiment for the determination of phosphoric acid (H)PO present in a cola soft drink. A 0.5 milliliters sample of cola is diluted to 125 mL. The measured absorbance is 0.262. Using a graph of absorbance versus H,PO concentration, the student determines that the diluted cola solution has a concentra- tion of 15.5 x 10 moles liter: a) Calculate the total moles of H,PO, present in 125 mL of solution with concentration 15.5 x 10 moles/liter. of solute Volume (n thers) X COncentration (in moletite)moles b) How many moles of H,PO4 are present in 0.5 mL of the undiluted cola. Only water is added in the dilution process. c) Calculate the concentration of HPO4 in moles/liter for the original cola solution. Recall: 0.5 milliliters 0.0005 Liters)

Answer 1

1 a)125 ml = 125 $^{^{^{}}}$ *10^-3 liters.

Therefore total moles of H₃PO₄ is = Volume of solution in liters *concentration of H₃PO_4.

   = 15.5_*10^-6_*125_*10^-3

  =1.9375_*10^-6 moles

b) The number of moles of solute does not change on dilution.Therefore no of moles before dilution is equal to no of moles after dilution.

The no of moles of H₃PO₄ in 0.5 ml of undiluted cola is = 1.9375_*10^-6 moles.

c) Concentration = no of moles of solute / volume of solution

     =1.9375_*10^-6/ 0.0005

= 3.875_*10^-3 moles/liter

2) a) Higher

b) Higher   

c) Unaffected

3) Molarity = Moles of solute/ liters of solution

= 0.0145 / 0.50

= 0.029 molar