2.2.3 Stoichiometry

• Stoichiometry is the quantitative study of relationships between reactants and products
• What is the molar ratio in the reaction \( 2H_2 + O_2 \rightarrow 2H_2O \)?

  2 : 1 : 2
• One mole contains \( 6.022 \times 10^{23} \) particles

  True
• Steps to calculate the mass of 3 moles of \( CO_2 \)

  1️⃣ Calculate the molar mass of \( CO_2 \)

  2️⃣ Multiply the molar mass by the number of moles
• What is the molar mass of \( CO_2 \)?

  44.01 g/mol
• In the reaction \( 2H_2 + O_2 \rightarrow 2H_2O \), how many moles of oxygen are needed to react with 2 moles of hydrogen?

  1 mole
• One mole of carbon contains \( 6.022 \times 10^{23} \) carbon atoms


  True
• Steps to calculate the molar mass of \( H_2O \)

  1️⃣ Find the atomic mass of hydrogen

  2️⃣ Find the atomic mass of oxygen

  3️⃣ Multiply hydrogen's atomic mass by 2

  4️⃣ Add the total mass of hydrogen to oxygen's atomic mass
• Atomic masses of elements are found in the periodic table.


  True
• Steps to calculate molar mass

  1️⃣ Identify the chemical formula

  2️⃣ Find atomic masses from the periodic table

  3️⃣ Multiply each atomic mass by the number of atoms

  4️⃣ Add all the masses together
• Reactants in a chemical reaction combine in a fixed molar ratio to form products


  True
• A mole is a unit used to measure the amount of a substance
• What is the value of Avogadro's number?

  $6.022 \times 10^{23}$
• Molar mass is the mass of one mole of a substance
• The molar mass of \( CO_2 \) is calculated by adding the atomic masses of 1 carbon atom and 2 oxygen atoms


  True
• One mole contains \( 6.022 \times 10^{23} \) particles, which is known as Avogadro's number
• What is the molar mass of \( H_2O \)?

  18.02 g/mol
• What are the units used to measure molar mass?

  grams per mole (g/mol)
• The molar mass of a substance is the mass of one mole
• What is the atomic mass of hydrogen?

  1.01 g/mol
• There are two hydrogen atoms in a molecule of H2O.


  True
• How many hydrogen atoms are in H2O?

  2
• To convert between moles and grams, use the molar mass of the substance.
• What is the formula to convert grams to moles?

  moles = grams / molar mass
• To convert from grams to moles, divide the mass in grams by the molar mass.


  True
• How many grams are in 2.5 moles of NaCl?

  146.1 grams
• The balanced equation for the combustion of methane is CH4 + 2O2 → CO2 + 2H2O.
• What does a balanced chemical equation ensure?

  Equal atoms on both sides
• Balancing chemical equations allows you to determine the quantitative relationships between reactants and products.
• In the reaction 2H2 + O2 → 2H2O, the molar ratio of hydrogen to oxygen is 2:1.


  True
• One mole contains exactly 6.022 × 1023 particles.
• What is the number of particles in one mole of a substance called?

  Avogadro's number
• One mole of carbon contains \(6.022 \times 10^{23}\) carbon atoms.

  True
• One mole is equal to \(6.022 \times 10^{23}\) particles
• Steps to calculate the molar mass of a compound

  1️⃣ Identify the chemical formula

  2️⃣ Look up atomic masses from the periodic table

  3️⃣ Multiply each atomic mass by the number of atoms

  4️⃣ Add up all the individual masses
• What is the atomic mass of oxygen?

  16.00 g/mol
• The molar mass of H2O is 18.02
• Match the element with its atomic mass:

  Hydrogen ↔️ 1.01 g/mol

  Oxygen ↔️ 16.00 g/mol
• What is the formula to convert moles to grams?

  grams = moles × molar mass
• To convert from moles to grams, multiply the number of moles by the molar mass.


  True