Molarity Worksheet Answers

Molarity Worksheet Answers

In chemistry, molarity is a fundamental concept that measures the concentration of a solution. It is defined as the number of moles of solute per liter of solution. Here, we will provide answers to a molarity worksheet, explaining the steps and calculations involved in solving each problem.

Problem 1: Calculate the molarity of a solution that contains 25.0 grams of sodium chloride (NaCl) in 500.0 mL of water.

Step 1: Determine the molar mass of NaCl. The molar mass of NaCl is 58.44 g/mol.

Step 2: Calculate the number of moles of NaCl. moles = mass of NaCl / molar mass of NaCl = 25.0 g / 58.44 g/mol = 0.428 mol

Step 3: Calculate the volume of the solution in liters. volume = 500.0 mL / 1000 mL/L = 0.5 L

Step 4: Calculate the molarity of the solution. molarity = moles of NaCl / volume of solution = 0.428 mol / 0.5 L = 0.856 M

Answer: The molarity of the solution is 0.856 M.

Problem 2: Calculate the molarity of a solution that contains 15.0 grams of glucose (C6H12O6) in 250.0 mL of water.

Step 1: Determine the molar mass of C6H12O6. The molar mass of C6H12O6 is 180.16 g/mol.

Step 2: Calculate the number of moles of C6H12O6. moles = mass of C6H12O6 / molar mass of C6H12O6 = 15.0 g / 180.16 g/mol = 0.083 mol

Step 3: Calculate the volume of the solution in liters. volume = 250.0 mL / 1000 mL/L = 0.25 L

Step 4: Calculate the molarity of the solution. molarity = moles of C6H12O6 / volume of solution = 0.083 mol / 0.25 L = 0.332 M

Answer: The molarity of the solution is 0.332 M.

Problem 3: A solution contains 20.0 grams of calcium chloride (CaCl2) in 750.0 mL of water. Calculate the molarity of the solution.

Step 1: Determine the molar mass of CaCl2. The molar mass of CaCl2 is 110.98 g/mol.

Step 2: Calculate the number of moles of CaCl2. moles = mass of CaCl2 / molar mass of CaCl2 = 20.0 g / 110.98 g/mol = 0.180 mol

Step 3: Calculate the volume of the solution in liters. volume = 750.0 mL / 1000 mL/L = 0.75 L

Step 4: Calculate the molarity of the solution. molarity = moles of CaCl2 / volume of solution = 0.180 mol / 0.75 L = 0.240 M

Answer: The molarity of the solution is 0.240 M.

Problem 4: A 0.50 M solution of potassium nitrate (KNO3) has a volume of 200.0 mL. Calculate the mass of KNO3 present in the solution.

Step 1: Determine the molar mass of KNO3. The molar mass of KNO3 is 101.10 g/mol.

Step 2: Calculate the number of moles of KNO3. moles = molarity x volume = 0.50 M x 0.2 L = 0.10 mol

Step 3: Calculate the mass of KNO3. mass = moles x molar mass = 0.10 mol x 101.10 g/mol = 10.11 g

Answer: The mass of KNO3 present in the solution is 10.11 g.

Notes:

• When calculating molarity, always express the volume in liters (L).
• The molar mass of a compound is the sum of the atomic masses of its constituent elements.
• When solving problems, always label your units and show your work.

Molarity Conversion Table:

Remember, molarity is a measure of concentration, so it’s essential to use the correct units when expressing molarity.

To wrap up this worksheet, we hope you now have a better understanding of how to calculate molarity and solve problems related to it. Practice makes perfect, so be sure to try more problems on your own to reinforce your knowledge.