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Sec. 9 Determination of phosphoric acid in cola using pH metric titrations

Prepared by

Hoda Abd El- Shafy Shilkamy Diab

Lecturer assistant of physical chemistry

Chemistry department – Faculty of Science – Sohag university

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around 0.055%

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H3PO4(aq) + H2O (l) H2PO4(aq) + H3O+ (aq) Equation 1

H2PO4(aq) + H2O (l) HPO42(aq) + H3O+ (aq) Equation 2

HPO42 (aq) + H2O (l) PO43(aq) + H3O+ (aq) Equation 3

Phosphoric acid dissociates as shown in these equations

Phosphoric acid dissociation constant

K1 7.11 x 10-3

K2 6.32 x 10-8

K3 7.10 x 10-13

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H3PO4 + NaOH → NaH2PO4 + H2O

NaH2PO4 + NaOH → Na2HPO4 + H2O

Na2HPO4 + NaOH Na3PO4 + H2O

Calcualtions ???