Multiple Choice
Determine the molarity of a solution formed by dissolving 97.7 g of LiBr in enough water to yield 750.0 mL of solution.
6. Chemical Quantities & Aqueous Reactions
Molarity
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How many milliliters of a 0.155 M KCl solution are required to contain 2.55 grams of KCl?
A
100 mL
B
250 mL
C
150 mL
D
200 mL
Verified step by step guidance1
First, calculate the molar mass of KCl. Potassium (K) has an atomic mass of approximately 39.10 g/mol, and Chlorine (Cl) has an atomic mass of approximately 35.45 g/mol. Add these values to find the molar mass of KCl.
Convert the mass of KCl from grams to moles using the formula: \( \text{moles of KCl} = \frac{\text{mass of KCl (g)}}{\text{molar mass of KCl (g/mol)}} \). Substitute the given mass of 2.55 grams and the calculated molar mass of KCl into this formula.
Use the molarity formula to find the volume of the solution needed: \( M = \frac{\text{moles of solute}}{\text{liters of solution}} \). Rearrange this formula to solve for the volume in liters: \( \text{liters of solution} = \frac{\text{moles of solute}}{M} \).
Substitute the moles of KCl calculated in step 2 and the given molarity of the solution (0.155 M) into the rearranged molarity formula to find the volume in liters.
Convert the volume from liters to milliliters by multiplying by 1000, since there are 1000 milliliters in a liter. This will give you the volume of the 0.155 M KCl solution required to contain 2.55 grams of KCl.
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