Ionic equilibrium

Question

Calculate the pH of the following solution : 

[For H3PO4

: K1 = 7.5 × 10–3 M ; K2 = 6.0 × 10–8 M ; K3 = 1.0 × 10–12 M]

[For H2CO3

: K1 = 4.0 × 10–7 M ; K2 = 5.0 × 10–11 M] (log2 = 0.3, log3 = 0.48)

(a) 40 ml of 0.050 M Na2CO3 + 50 ml of 0.040 M HCl;

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