Multiple Choice
What volume of solution is prepared when 25.0 g of ethanol (C₂H₅OH) is added to enough water to make a 0.750 M ethanol solution? (Molar mass of ethanol = 46.08 g/mol)
6. Chemical Quantities & Aqueous Reactions
Molarity
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A KOH solution is prepared by dissolving 8.33 g of KOH in enough water to make 840 mL of solution. What is the molarity of the solution?
A
0.176 M
B
0.500 M
C
0.250 M
D
0.098 M
Verified step by step guidance1
Calculate the molar mass of KOH by adding the atomic masses of potassium (K), oxygen (O), and hydrogen (H). Use the periodic table to find these values: K = 39.10 g/mol, O = 16.00 g/mol, H = 1.01 g/mol. The molar mass of KOH is the sum of these values.
Convert the mass of KOH from grams to moles using the formula: \( \text{moles of KOH} = \frac{\text{mass of KOH (g)}}{\text{molar mass of KOH (g/mol)}} \). Substitute the given mass of KOH (8.33 g) and the calculated molar mass from the previous step.
Convert the volume of the solution from milliliters to liters, since molarity is expressed in moles per liter. Use the conversion: \( 1 \text{ L} = 1000 \text{ mL} \). Therefore, \( \text{volume in liters} = \frac{840 \text{ mL}}{1000} \).
Calculate the molarity of the KOH solution using the formula: \( \text{Molarity (M)} = \frac{\text{moles of solute}}{\text{volume of solution in liters}} \). Substitute the moles of KOH and the volume in liters obtained from the previous steps.
Compare the calculated molarity with the given options to determine the correct answer.
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