Molarity Calculation with Stoichiometry: Real-World Examples

📚 Quick Study Guide

🔍 Molarity (M) is defined as the number of moles of solute per liter of solution: $M = \frac{moles \ of \ solute}{liters \ of \ solution}$.

⚖️ Stoichiometry involves using the mole ratio from balanced chemical equations to calculate the amounts of reactants and products in a chemical reaction.

🧪 Steps to solve molarity stoichiometry problems:
• 1. Balance the chemical equation.
• 2. Convert given quantities to moles.
• 3. Use the mole ratio from the balanced equation to find the moles of the desired substance.
• 4. Convert moles back to the desired units (e.g., grams, liters of solution).

💡 Remember to pay attention to significant figures in your calculations.

Practice Quiz

1. What is the molarity of a solution prepared by dissolving 11.6 g of NaCl in enough water to make 1.50 L of solution? (Molar mass of NaCl = 58.44 g/mol)
1. 0.133 M
2. 0.266 M
3. 0.773 M
4. 1.33 M
2. How many grams of $Ca(OH)_2$ are needed to neutralize 25.0 mL of 0.100 M $HCl$ solution? (Molar mass of $Ca(OH)_2$ = 74.09 g/mol)
1. 0.0926 g
2. 0.0463 g
3. 0.185 g
4. 0.0232 g
3. If 30.0 mL of 1.0 M $NaOH$ is required to neutralize 10.0 mL of an $H_2SO_4$ solution, what is the molarity of the $H_2SO_4$ solution?
1. 1.5 M
2. 3.0 M
3. 0.15 M
4. 0.33 M
4. What volume of 0.250 M $KCl$ solution is needed to react completely with 5.0 g of $AgNO_3$? (Molar mass of $AgNO_3$ = 169.87 g/mol)
1. 118 mL
2. 236 mL
3. 59 mL
4. 29.5 mL
5. Consider the reaction: $2H_2(g) + O_2(g) \rightarrow 2H_2O(g)$. If 4.0 g of $H_2$ reacts with excess $O_2$, what mass of $H_2O$ is produced? (Molar mass of $H_2$ = 2.02 g/mol, Molar mass of $H_2O$ = 18.02 g/mol)
1. 18.0 g
2. 36.0 g
3. 72.0 g
4. 9.0 g
6. A 20.0 mL sample of 0.50 M $BaCl_2$ is mixed with 30.0 mL of 0.25 M $Na_2SO_4$. What is the concentration of $Ba^{2+}$ ions after the reaction is complete? (Assume the reaction goes to completion and the volumes are additive.)
1. 0.05 M
2. 0.10 M
3. 0.20 M
4. 0.25 M
7. How many liters of $O_2$ gas at STP are required to completely react with 10.0 g of $C_3H_8$? (Molar mass of $C_3H_8$ = 44.09 g/mol, Reaction: $C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O$, Molar volume of gas at STP = 22.4 L/mol)
1. 5.09 L
2. 25.45 L
3. 11.2 L
4. 127.25 L