Multiple Choice
Calculate mass (grams) needed for the following base equivalent: 0.18 mEq of Mg(OH)2.
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10. Acids and Bases
Acid-Base Equivalents
Multiple Choice
Determine volume (mL) needed to prepare a 0.73 g of Ca(OH)2 solution with 1.25 N.
A
7.9 mL
B
20 mL
C
1.6 mL
D
16 mL
Verified step by step guidance1
Understand the concept of normality (N), which is a measure of concentration equivalent to molarity multiplied by the number of equivalents per mole of solute. For Ca(OH)_2, which is a strong base, the number of equivalents is 2 because it can donate 2 hydroxide ions (OH^-) per formula unit.
Calculate the molar mass of Ca(OH)_2. The atomic masses are approximately: Ca = 40.08 g/mol, O = 16.00 g/mol, and H = 1.01 g/mol. Therefore, the molar mass of Ca(OH)_2 is 40.08 + 2(16.00 + 1.01) g/mol.
Determine the number of moles of Ca(OH)_2 in 0.73 g by using the formula: moles = mass (g) / molar mass (g/mol).
Calculate the equivalents of Ca(OH)_2 using the formula: equivalents = moles × number of equivalents per mole. Since Ca(OH)_2 has 2 equivalents per mole, multiply the moles by 2.
Use the normality equation to find the volume: Normality (N) = equivalents / volume (L). Rearrange to solve for volume: volume (L) = equivalents / Normality. Convert the volume from liters to milliliters by multiplying by 1000.
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