Step 1
The reaction:
Ca(OH)2 (aq) + 2 HBr (aq) => CaBr2 (aq) + 2 H2O (l) (compelted and balanced)
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Step 2
Information provided:
0.0105 M HBr
125 mL of 0.0100 M Ca(OH)2
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Step 3
The number of moles of Ca(OH)2:
Molarity (mol/L) = moles of Ca(OH)2/volume of the solution (L)
Volume = 125 mL x (1 L/1000 mL) = 0.125 L
Therefore,
Molarity x volume (L) = moles
0.0100 mol/L x 0.125 L = 1.25x10^-3 moles of Ca(OH)2
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Step 4
The number of moles of HBr, by stoichiometry:
Ca(OH)2 (aq) + 2 HBr (aq) => CaBr2 (aq) + 2 H2O (l)
1 mol Ca(OH)2 ------ 2 moles HBr
1.25x10^-3 moles ------ X
X = 1.25x10^-3 moles x 2 moles HBr/1 mol Ca(OH)2
X = 2.5x10^-3 moles HBr
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Step 5
The volume of HBr needed:
Molarity = moles of HBr/volume of solution (L)
Volume = moles of HBr/molarity
Volume = 2.5x10^-3 moles HBr/0.0105 mol/L
Volume = 0.238 L
Volume = 0.238 L x (1000 mL/1 L) = 238 mL
Answer: 238 mL or 0.238 L (there are no matches)
