Multiple Choice
What is the concentration of K+ ions in a 0.15 M solution of K2S?
6. Chemical Quantities & Aqueous Reactions
Molarity
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What is the molar concentration of a solution prepared by dissolving 25.75 g of NaOH in water to produce 500.0 mL of solution?
A
0.64 M
B
0.32 M
C
1.29 M
D
2.58 M
Verified step by step guidance1
Calculate the molar mass of NaOH by adding the atomic masses of sodium (Na), oxygen (O), and hydrogen (H). Use the periodic table to find these values: Na = 22.99 g/mol, O = 16.00 g/mol, H = 1.01 g/mol.
Add the atomic masses to find the molar mass of NaOH: Molar mass of NaOH = 22.99 g/mol + 16.00 g/mol + 1.01 g/mol.
Determine the number of moles of NaOH by dividing the mass of NaOH by its molar mass: \( \text{moles of NaOH} = \frac{25.75 \text{ g}}{\text{molar mass of NaOH}} \).
Convert the volume of the solution from milliliters to liters, since molarity is expressed in moles per liter: \( 500.0 \text{ mL} = 0.5000 \text{ L} \).
Calculate the molarity of the solution by dividing the number of moles of NaOH by the volume of the solution in liters: \( \text{Molarity} = \frac{\text{moles of NaOH}}{0.5000 \text{ L}} \).
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