Multiple Choice
What is the molarity of a solution prepared by dissolving 5 moles of solute in 2 liters of solution?
6. Chemical Quantities & Aqueous Reactions
Molarity
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What is the mass of NaCl required to prepare 500 mL of a 0.5 M NaCl aqueous solution?
A
29.2 g
B
7.3 g
C
58.4 g
D
14.6 g
Verified step by step guidance1
Understand the concept of molarity, which is defined as the number of moles of solute per liter of solution. The formula for molarity is \( M = \frac{n}{V} \), where \( M \) is the molarity, \( n \) is the number of moles, and \( V \) is the volume in liters.
Convert the volume of the solution from milliliters to liters. Since 1 liter is equal to 1000 milliliters, 500 mL is equivalent to 0.5 L.
Use the molarity formula to find the number of moles of NaCl required. Rearrange the formula to \( n = M \times V \). Substitute \( M = 0.5 \) M and \( V = 0.5 \) L into the equation to calculate \( n \).
Determine the molar mass of NaCl. Sodium (Na) has an atomic mass of approximately 23 g/mol, and chlorine (Cl) has an atomic mass of approximately 35.5 g/mol. Therefore, the molar mass of NaCl is \( 23 + 35.5 = 58.5 \) g/mol.
Calculate the mass of NaCl required using the formula \( \text{mass} = n \times \text{molar mass} \). Substitute the number of moles calculated in step 3 and the molar mass from step 4 into this formula to find the mass of NaCl needed.
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