Multiple Choice
What is the coefficient for H2O(l) when the reaction PbO2(s) + I2(s) → Pb2+(aq) + IO3−(aq) is balanced in an acidic aqueous solution?
6. Chemical Quantities & Aqueous Reactions
Balancing Redox Reactions: Acidic Solutions
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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
Verified step by step guidance1
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.
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.
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.
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).
Convert the volume from liters to milliliters by multiplying by 1000, as the final answer should be in mL.
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