How many grams of KCl are needed to prepare 250 mL of a 0.5 M solution? (2023) 2

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Question: How many grams of KCl are needed to prepare 250 mL of a 0.5 M solution? (2023) 2023

Options:

Correct Answer: 7.45 g

Exam Year: 2023

Solution:

Molar mass of KCl = 74.55 g/mol. Grams = Molarity * Volume (L) * Molar mass = 0.5 M * 0.25 L * 74.55 g/mol = 9.31 g.

How many grams of KCl are needed to prepare 250 mL of a 0.5 M solution? (2023) 2023

How many grams of KCl are needed to prepare 250 mL of a 0.5 M solution? (2023) 2023

Step 1: Understand that Molarity (M) is the number of moles of solute per liter of solution.
Step 2: Convert the volume from milliliters to liters. 250 mL is equal to 0.25 L.
Step 3: Identify the molar mass of KCl, which is 74.55 g/mol.
Step 4: Use the formula to find the grams needed: Grams = Molarity * Volume (L) * Molar mass.
Step 5: Plug in the values: Grams = 0.5 M * 0.25 L * 74.55 g/mol.
Step 6: Calculate the result: Grams = 0.5 * 0.25 * 74.55 = 9.31 g.

Molarity Calculation – Understanding how to calculate the amount of solute needed based on molarity, volume, and molar mass.
Unit Conversion – Converting volume from mL to L to use in molarity calculations.
Molar Mass – Using the correct molar mass of KCl to find the mass needed for the solution.