Molarity Problems Worksheet With Answers

Molarity Problems Worksheet With Answers

Molarity is a unit of concentration that describes the amount of a substance dissolved in a solution. It is defined as the number of moles of a substance per liter of solution. Calculating molarity can be a challenging task for many students, but with practice, it becomes easier. Here is a worksheet with answers to help you practice calculating molarity.

Problem 1

A 0.50 M solution of sodium chloride (NaCl) contains 0.50 moles of NaCl per liter of solution. If you have 250 mL of a 0.50 M NaCl solution, how many moles of NaCl are present?

📝 Note: First, convert the volume from milliliters to liters.

• 250 mL = 0.25 L
• Number of moles = Molarity x Volume (in liters)
• Number of moles = 0.50 M x 0.25 L
• Number of moles = 0.125 mol

Problem 2

A solution of calcium chloride (CaCl2) contains 75 grams of CaCl2 in 2 liters of solution. If the molar mass of CaCl2 is 111 g/mol, what is the molarity of the solution?

📝 Note: First, calculate the number of moles of CaCl2.

• Number of moles = Mass of CaCl2 / Molar mass of CaCl2
• Number of moles = 75 g / 111 g/mol
• Number of moles = 0.675 mol
• Molarity = Number of moles / Volume (in liters)
• Molarity = 0.675 mol / 2 L
• Molarity = 0.3375 M

Problem 3

A 0.10 M solution of potassium nitrate (KNO3) contains 0.10 moles of KNO3 per liter of solution. If you need 0.50 moles of KNO3 for an experiment, how many liters of the 0.10 M KNO3 solution do you need?

📝 Note: Rearrange the molarity equation to solve for volume.

• Volume = Number of moles / Molarity
• Volume = 0.50 mol / 0.10 M
• Volume = 5 L

Problem 4

A solution of glucose (C6H12O6) contains 180 grams of glucose in 4 liters of solution. If the molar mass of glucose is 180 g/mol, what is the molarity of the solution?

📝 Note: First, calculate the number of moles of glucose.

• Number of moles = Mass of glucose / Molar mass of glucose
• Number of moles = 180 g / 180 g/mol
• Number of moles = 1 mol
• Molarity = Number of moles / Volume (in liters)
• Molarity = 1 mol / 4 L
• Molarity = 0.25 M

Problem 5

A 0.20 M solution of sodium hydroxide (NaOH) contains 0.20 moles of NaOH per liter of solution. If you need 0.15 moles of NaOH for an experiment, how many liters of the 0.20 M NaOH solution do you need?

📝 Note: Rearrange the molarity equation to solve for volume.

• Volume = Number of moles / Molarity
• Volume = 0.15 mol / 0.20 M
• Volume = 0.75 L

Conclusion

Molarity is an essential concept in chemistry that describes the concentration of a solution. With practice, you can become proficient in calculating molarity. Remember to always check your units and conversion factors to ensure accurate calculations.

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