Multiple Choice
How many milliliters of 0.325 M HCl are needed to react with 16.2 g of magnesium metal?
2 HCl (aq) + Mg (s) → MgCl2 + H2 (g)
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9. Solutions
Solution Stoichiometry
Multiple Choice
What is the molar concentration of a hydrobromic acid solution if it takes 34.12 mL of HBr to completely neutralize 82.56 mL of 0.156 M Ca(OH)2?
2 HBr (aq) + Ca(OH)2 (aq) → CaBr2 (aq) + 2 H2O (l)
A
0.326 M
B
0.755 M
C
0.811 M
D
1.38 M
E
1.85 M
Verified step by step guidance1
Start by writing the balanced chemical equation for the reaction: 2 HBr (aq) + Ca(OH)2 (aq) → CaBr2 (aq) + 2 H2O (l). This equation shows that 2 moles of HBr react with 1 mole of Ca(OH)2.
Determine the moles of Ca(OH)2 present in the solution using its molar concentration and volume. Use the formula: moles = concentration (M) × volume (L). Convert the volume from mL to L by dividing by 1000.
Using the stoichiometry from the balanced equation, calculate the moles of HBr required to completely neutralize the moles of Ca(OH)2. Since 2 moles of HBr are needed for every mole of Ca(OH)2, multiply the moles of Ca(OH)2 by 2.
Calculate the molar concentration of the HBr solution using the moles of HBr and the volume of HBr solution used. Use the formula: concentration (M) = moles / volume (L). Again, convert the volume from mL to L by dividing by 1000.
Compare the calculated molar concentration of HBr with the given options to identify the correct answer.
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