Multiple Choice
What is the integer value of the molarity of a CH3OH solution with a concentration of 1.225 M?
6. Chemical Quantities & Aqueous Reactions
Molarity
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A solution is prepared by dissolving 23.7 g of CaCl2 in 375 g of water. The density of the resulting solution is 1.05 g/mL. What is the molarity of Cl⁻ ions in this solution?
A
1.68 M
B
0.66 M
C
0.84 M
D
0.42 M
Verified step by step guidance1
Calculate the moles of CaCl₂: First, determine the molar mass of CaCl₂ by adding the atomic masses of calcium (Ca) and chlorine (Cl). The molar mass of CaCl₂ is approximately 40.08 g/mol for Ca and 35.45 g/mol for each Cl, giving a total of 110.98 g/mol for CaCl₂. Use the formula: \( \text{moles of CaCl}_2 = \frac{\text{mass of CaCl}_2}{\text{molar mass of CaCl}_2} \).
Determine the total volume of the solution: Use the density of the solution to find its volume. The density is given as 1.05 g/mL. The total mass of the solution is the sum of the mass of water and the mass of CaCl₂, which is 375 g + 23.7 g. Use the formula: \( \text{volume} = \frac{\text{mass}}{\text{density}} \).
Calculate the moles of Cl⁻ ions: Since each formula unit of CaCl₂ produces two Cl⁻ ions, multiply the moles of CaCl₂ by 2 to find the moles of Cl⁻ ions.
Calculate the molarity of Cl⁻ ions: Molarity is defined as moles of solute per liter of solution. Use the formula: \( \text{Molarity} = \frac{\text{moles of Cl}^-}{\text{volume of solution in liters}} \). Convert the volume from mL to L by dividing by 1000.
Review the calculation: Ensure all units are consistent and check each step for accuracy to confirm the molarity of Cl⁻ ions in the solution.
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