Part A Calculate the [H3O+] of the following polyprotic acid solution: 0.300M H3PO4. Express your answer using two significant figures. Part B Calculate the pH of this solution.
Express your answer using one decimal place.
Part C Calculate the [H3O+] and pH of the following polyprotic acid solution: 0.310M H2C2O4.
Express your answer using two significant figures.
Part D Calculate the pH of this solution.
Express your answer using two decimal places.

A. [H₃O⁺] = 0.900 M

B. pH = 0.0 to one decimal place

C. [H₃O⁺] = 0.620 M

D. pH = 0.21 to two decimal places

Explanation:

A. Equation for the complete dissociation of H₃PO₄ is given below:

H₃PO₄(s) + 3H₂O(l) > PO₄³⁻(aq) + 3H₃O⁺(aq)

From the equation of reaction, one mole of H₃PO₄ produces 3 moles of H₃O⁺

Therefore, [H₃O⁺] = 3 * 0.300M = 0.900 M

B. pH = -log[H₃O⁺]

pH = - log(0.900)

pH = -log (9 * 10⁻¹)

pH = 0.0 to one decimal place

C. Equation for the complete dissociation of H₂C₂O₄ is given below:

H₂C₂O₄(s) + 2H₂O(l) > C₂O₄⁻(aq) + 2H₃O⁺

From the equation of reaction, one mole of H₂C₂O₄ produces 3 moles of H₃O⁺

Therefore, [H₃O⁺] = 2 * 0.310 M = 0.620 M

D. pH = -log[H₃O⁺]

pH = -log(0.620)

pH = -log(0.62 * 10⁻¹)

pH = 0.21 to two decimal places

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