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)
13. Solutions
Solution Stoichiometry
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)
A
33 mL
B
742 mL
C
872 mL
D
3321 mL
E
4100 mL
Verified step by step guidance1
First, determine the molar mass of magnesium (Mg). Magnesium has an atomic mass of approximately 24.31 g/mol.
Calculate the number of moles of magnesium using the formula: \( \text{moles of Mg} = \frac{\text{mass of Mg}}{\text{molar mass of Mg}} \). Substitute the given mass of magnesium (16.2 g) and its molar mass (24.31 g/mol) into the formula.
Use the stoichiometry of the balanced chemical equation \( 2 \text{HCl} + \text{Mg} \rightarrow \text{MgCl}_2 + \text{H}_2 \) to find the moles of HCl needed. According to the equation, 2 moles of HCl react with 1 mole of Mg. Therefore, multiply the moles of Mg by 2 to find the moles of HCl required.
Calculate the volume of 0.325 M HCl solution needed using the formula: \( \text{Volume (L)} = \frac{\text{moles of HCl}}{\text{molarity of HCl}} \). Substitute the moles of HCl and the molarity (0.325 M) into the formula.
Convert the volume from liters to milliliters by multiplying the result by 1000, since 1 L = 1000 mL.
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