Moles & Molecules
What is the number of particles in one mole of any substance?
Avogadro's number
Balance the equation:
CH₄ + O₂ → CO₂ + H₂O
CH₄ + 2 O₂ → CO₂ + 2 H₂O
In a chemical reaction, the reactant that is consumed first and limits how much product can be formed is called the
limiting reactant
If 10 grams of sodium chloride (NaCl) are dissolved in water, how many moles of NaCl are present?
10 g NaCl ÷ 58.44 g/mol = 0.171 moles of NaCl
How many moles are in 22.4 liters of a gas at standard temperature and pressure?
1 mole
Balance the equation:
C₆H₆ + O₂ → CO₂ + H₂O
2 C₆H₆ + 15 O₂ → 12 CO₂ + 6 H₂O
If you have 3 moles of H₂ and 2 moles of O₂, which is the limiting reactant in the reaction:
2 H₂ + O₂ → 2 H₂O?
H₂
How many moles of oxygen are in 8 grams of O₂?
8 g ÷ 32 g/mol = 0.25 moles of O₂
How many grams are in 1 mole of oxygen gas (O₂)?
32 grams
What is the coefficient of oxygen (O₂) when this equation is balanced:
C₄H₁₀ + O₂ → CO₂ + H₂O
13/2 or 6.5 O₂
If 10 grams of magnesium react with excess oxygen, how many grams of magnesium oxide will be formed?
First, calculate moles of magnesium (10 g ÷ 24.305 g/mol = 0.411 moles). Then, use the stoichiometry of the reaction to find the mass of magnesium oxide (0.411 moles Mg × 40.304 g/mol = 16.56 grams).
What is the mass of 2.5 moles of sulfur dioxide (SO₂)?
2.5 moles × 64.06 g/mol = 160.15 grams of SO₂
If you have 3.01 × 10²³ molecules of water (H₂O), how many moles do you have?
0.5 moles
Balance the equation:
Fe + O₂ → Fe₂O₃
4 Fe + 3 O₂ → 2 Fe₂O₃
In a reaction where 5 moles of nitrogen gas (N₂) react with 15 moles of hydrogen gas (H₂), what is the limiting reactant?
Nitrogen gas (N₂) because the stoichiometry is 1:3, so only 15 moles of H₂ are needed to fully react with 5 moles of N₂).
How many liters of CO₂ are produced when 5 grams of calcium carbonate (CaCO₃) are heated in excess oxygen? The balanced equation is:
CaCO₃ → CaO + CO₂
5 g CaCO₃ ÷ 100.09 g/mol = 0.05 moles of CaCO₃. Since the reaction is 1:1, 0.05 moles of CO₂ are produced. 0.05 moles CO₂ × 22.4 L/mol = 1.12 L of CO₂.
Calculate the number of atoms in 2 moles of NaCl.
2 × 6.022 × 10²³ atoms of Na + 2 × 6.022 × 10²³ atoms of Cl = 2 × 6.022 × 10²³ atoms × 2 = 2.4044 × 10²⁴ atoms.
Balance the equation:
C₈H₁₀ + O₂ → CO₂ + H₂O
2 C₈H₁₀ + 25 O₂ → 16 CO₂ + 10 H₂O
You have 3 moles of hydrogen and 2 moles of oxygen. How many grams of water can be produced?
The limiting reagent is oxygen. Since the reaction is 2 H₂ + O₂ → 2 H₂O, oxygen will limit the reaction. Use stoichiometry to find the mass of water: 2 moles of O₂ react to produce 2 moles of H₂O. Therefore, 2 moles of H₂O × 18.015 g/mol = 36.03 grams of H₂O.
How many grams of NaOH are required to react with 10 grams of H₂SO₄ in the reaction:
H₂SO₄ + 2 NaOH → Na₂SO₄ + 2 H₂O?
10 g H₂SO₄ ÷ 98.08 g/mol = 0.102 moles H₂SO₄. From the balanced equation, 1 mole H₂SO₄ reacts with 2 moles NaOH, so 0.102 moles × 2 = 0.204 moles NaOH. 0.204 moles × 40.00 g/mol = 8.16 grams of NaOH.