Phosphoric acid H₃PO₄ has many industrial uses and is often found in some cola drinks. If you had 25.0 mL of a 0.200 M solution of H₃PO₄, how many mL of a 0.400 M solution of Ba(OH)₂ would be required to neutralize the acid according to the following reaction? ?2 H₃PO₄ (aq) + 3 Ba(OH)₂ (aq) → Ba₃(PO₄)₂ (s) + 6 H₂O (l)

• A. 25.0 mL
• B. 18.8 mL
• C. 8.33 mL
• D. 12.5 mL
• E. 75.0 mL

Answer: (B)

Verified step by step guidance

1. First, write down the balanced chemical equation for the reaction: 2 H3PO4 (aq) + 3 Ba(OH)2 (aq) → Ba3(PO4)2 (s) + 6 H2O (l). This equation tells us that 2 moles of phosphoric acid react with 3 moles of barium hydroxide.
2. Calculate the number of moles of H3PO4 in the given solution. Use the formula: moles = concentration (M) × volume (L). Convert the volume from mL to L by dividing by 1000.
3. Using the stoichiometry of the balanced equation, determine the moles of Ba(OH)2 required to react with the calculated moles of H3PO4. According to the equation, 2 moles of H3PO4 react with 3 moles of Ba(OH)2, so use the ratio 3/2 to find the moles of Ba(OH)2.
4. Calculate the volume of the 0.400 M Ba(OH)2 solution needed to provide the required moles of Ba(OH)2. Use the formula: volume (L) = moles / concentration (M).
5. Convert the volume from liters to milliliters by multiplying by 1000, as the final answer should be in mL.