Multiple Choice
A stock solution of Pb(NO3)2 (315 mL, 2.5 M) contains how many Pb²⁺ ions and how many nitrate ions?
6. Chemical Quantities & Aqueous Reactions
Molarity
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What is the molarity of Na+ ions in a solution prepared by dissolving 0.5 moles of NaCl in 1 liter of water?
A
1.0 M
B
0.25 M
C
2.0 M
D
0.5 M
Verified step by step guidance1
Understand that molarity (M) is defined as the number of moles of solute per liter of solution. The formula for molarity is: M = \( \frac{\text{moles of solute}}{\text{liters of solution}} \).
Identify the solute in the problem, which is NaCl. When NaCl dissolves in water, it dissociates into Na+ and Cl- ions.
Recognize that 1 mole of NaCl will produce 1 mole of Na+ ions and 1 mole of Cl- ions because NaCl dissociates completely in water.
Given that there are 0.5 moles of NaCl dissolved in 1 liter of water, calculate the molarity of Na+ ions using the formula: M = \( \frac{0.5 \text{ moles of Na}^+}{1 \text{ liter of solution}} \).
Conclude that the molarity of Na+ ions in the solution is 0.5 M, as the number of moles of Na+ ions is equal to the number of moles of NaCl dissolved.
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