Prelaboratory assignment Exp. 8 Phosphoric Acid in Cola Date:- Lab Section I. Th
ID: 556534 • Letter: P
Question
Prelaboratory assignment Exp. 8 Phosphoric Acid in Cola Date:- Lab Section I. The phosphoric acid in a 100.00-mL sample of Cola drink was titrated with 0,1025 NaOH. If the first equivalence point occurred after 16.11 ml of base was added, and the second equivalence point molar concentrations of H,PO, in the Cola sample based on: v occured after 32.55 ml of base was added, calculate the a. The first equivalence point b. The second equivalence point What is the average concentration? c. 2. average concentration in question 1c, if you were able to titrate to the third Based on the equivalence point of H PO4, What would the total volume of NaOH you would need?Explanation / Answer
Net ionic equation for the titration up to the 1st equivalence point
H3PO4+NaOHNaH2PO4+H2O
Volume of NaOH needed to reach the 1st equivalence point = 16.11 ml
a) molarity of the phosphoric acid based on the 1st equivalence point
M1V1/n1=M2V2/n2 n1=n2 =1
M1V1 = M2V2
molarity of the phosphoric acid =M1 =M2V2/V1= 0.1025 x 16.11/100= 0.0165
Net ionic equation for the titration up to the 2nd equivalence point
H3PO4 + 2NaOH Na2HPO4 + 2H2O
M1V1/n1=M2V2/n2 n1=1 n2 =2
b)molarity of the phosphoric acid =M1 = (M2V2/n2) x (n1/V1 )= (01025 x 32.55/2) x (1/100)= 0.0167
c) average concentration= (0.0165+0.0167)/2= 0.0166
2) H3PO4 + 3NaOH Na3PO4 + 2H2O
M1 = 0.166 V1= 100 n1=1 M2=0.1025 V2=? n2=3
Volume of NaOH required to get 3rd equivalent point
V2 = (M1V1/n1) x (n2/M2) = (0.0166 x 100/1) x (3/0.1025) = 48.58 ml