Multiple Choice
What is the molarity of Fe(SCN)²⁺ in a solution with an absorbance of 0.243, prepared by mixing 2.5 mL of 0.200 M Fe(NO₃)₃, 0.4 mL of 0.002 M NaSCN, and 7.1 mL of 0.10 M HNO₃?
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6. Chemical Quantities & Aqueous Reactions
Molarity
Multiple Choice
How many grams of calcium nitrate (Ca(NO3)2) are required to prepare 500.0 mL of a 0.500 M calcium nitrate solution?
A
82.0 grams
B
10.25 grams
C
20.5 grams
D
41.0 grams
Verified step by step guidance1
Determine the molarity formula: Molarity (M) = moles of solute / liters of solution.
Convert the volume of the solution from milliliters to liters: 500.0 mL = 0.500 L.
Use the molarity formula to find the moles of calcium nitrate needed: moles = Molarity (M) × Volume (L).
Calculate the molar mass of calcium nitrate, Ca(NO3)2. Add the atomic masses of all atoms: Ca = 40.08 g/mol, N = 14.01 g/mol, O = 16.00 g/mol. Molar mass = 40.08 + 2(14.01 + 3(16.00)).
Convert moles of calcium nitrate to grams using its molar mass: grams = moles × molar mass.
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