Stoichiometry examples problems

📚 Quick Study Guide

• ⚖️ Balancing Equations: Ensure the number of atoms for each element is the same on both sides of the equation.
• 🔢 Moles: The mole is the SI unit for the amount of substance. 1 mole = $6.022 \times 10^{23}$ entities (Avogadro's number).
• 🧪 Molar Mass: The mass of one mole of a substance, usually expressed in grams per mole (g/mol). Calculate it by summing the atomic masses of all atoms in the chemical formula.
• stoichiometry ratios stoichiometric ratio of reactant A to product B is found using the coefficients in the balanced chemical equation. This represents the ratio of moles of reactant A needed to produce a particular number of moles of product B.
• 📐 Stoichiometric Calculations: Use the balanced equation to determine mole ratios between reactants and products. Convert given masses to moles, apply the mole ratio, and convert back to the desired units.
• 💡 Limiting Reactant: The reactant that is completely consumed in a reaction. It determines the maximum amount of product that can be formed.
• 💯 Percent Yield:** (Actual Yield / Theoretical Yield) × 100%

🧪 Practice Quiz

1. Question 1: What is the coefficient for oxygen when the following equation is properly balanced? $C_2H_6 + O_2 \rightarrow CO_2 + H_2O$
   1. A) 2
   2. B) 3
   3. C) 7
   4. D) 14
2. Question 2: How many moles are present in 56 grams of Iron (Fe)? (Molar mass of Fe = 56 g/mol)
   1. A) 0.5 moles
   2. B) 1 mole
   3. C) 2 moles
   4. D) 3 moles
3. Question 3: If 10 grams of $H_2$ react with excess $O_2$, how many grams of $H_2O$ are produced? (Molar mass: $H_2$ = 2 g/mol, $H_2O$ = 18 g/mol; Reaction: $2H_2 + O_2 \rightarrow 2H_2O$)
   1. A) 45 g
   2. B) 90 g
   3. C) 180 g
   4. D) 360 g
4. Question 4: For the reaction $N_2 + 3H_2 \rightarrow 2NH_3$, if you start with 6 moles of $H_2$, how many moles of $NH_3$ can be produced?
   1. A) 2 moles
   2. B) 3 moles
   3. C) 4 moles
   4. D) 6 moles
5. Question 5: What is the limiting reactant when 5 moles of $H_2$ react with 2 moles of $N_2$ according to the following equation? $N_2 + 3H_2 \rightarrow 2NH_3$
   1. A) $N_2$
   2. B) $H_2$
   3. C) $NH_3$
   4. D) None of the above
6. Question 6: If the theoretical yield of a reaction is 20 grams and the actual yield is 15 grams, what is the percent yield?
   1. A) 25%
   2. B) 50%
   3. C) 75%
   4. D) 100%
7. Question 7: How many grams of NaCl are produced if 10 grams of Na react with excess $Cl_2$? (Molar mass: Na = 23 g/mol, NaCl = 58.5 g/mol; Reaction: $2Na + Cl_2 \rightarrow 2NaCl$)
   1. A) 12.7 g
   2. B) 25.4 g
   3. C) 50.8 g
   4. D) 101.6 g