1.5.3 Chemical Equations and Calculations

• Balancing a chemical equation ensures mass is conserved.


  True
• Steps to balance a chemical equation

  1️⃣ Count the number of atoms for each element on both sides

  2️⃣ Use coefficients to equalize the number of atoms for each element

  3️⃣ Recount and adjust until balanced
• Molar mass is calculated by adding the atomic masses of all atoms in a substance.


  True
• What is the molar mass of CO2?

  44 g/mol
• What is molar mass measured in?

  grams per mole
• Steps to calculate molar mass

  1️⃣ Identify the atomic masses of each element

  2️⃣ Multiply each atomic mass by its subscript

  3️⃣ Add all the masses together
• The molar mass of Mg is 24 g/mol.
• What is the mole ratio of Mg to MgO in the balanced equation 2 Mg + O2 → 2 MgO?

  1:1
• How many moles of HCl are needed to react completely with 3 moles of Na in the equation 2 Na + 2 HCl → 2 NaCl + H2?

  3 moles
• Balancing a chemical equation is essential to determine the mole ratios between reactants and products.
• Balancing chemical equations ensures the number of atoms of each element is the same on both sides of the equation.
• Molar mass relates the mass of a substance to its amount in moles.

  True
• Match the steps in mass-mass conversions with their descriptions:

  Balance the chemical equation ↔️ Determine the stoichiometric relationships

  Convert known mass to moles ↔️ Use molar mass to find moles

  Use mole ratio from balanced equation ↔️ Find moles of other substance

  Convert moles to mass ↔️ Use molar mass to find mass
• The balanced reaction 2 Mg + O2 → 2 MgO has a 1:1 mole ratio between Mg and MgO.


  True
• What are mole-mole conversions used for?

  Convert moles of substances
• What is the relationship between mole-mole conversions and balanced chemical equations?

  Use mole ratios
• Steps for mole-mole conversions

  1️⃣ Balance the chemical equation

  2️⃣ Determine the mole ratios

  3️⃣ Convert the known moles
• The Ideal Gas Law relates pressure, volume, moles, and temperature of a gas.

  True
• At STP, 1 mole of any gas occupies a volume of 22.4 L.
• A chemical equation shows the reactants and the products
• Match the characteristic with the type of equation:

  Ensures mass is conserved ↔️ Balanced equation

  Does not accurately represent the reaction ↔️ Unbalanced equation
• To calculate molar mass, first identify the atomic masses of each element
• The molar mass of H2O is 18
• Match the type of equation with its characteristic:

  Balanced equation ↔️ Coefficients ensure atoms match

  Unbalanced equation ↔️ Mass is not conserved
• Molar mass is calculated by adding the atomic masses of all elements in a chemical formula.


  True
• The atomic mass of oxygen is 16 g/mol.
• Stoichiometry involves studying quantitative relationships in chemical reactions.
• To convert moles to mass, multiply the number of moles by the molar mass.


  True
• Steps to calculate mass-mass conversions in stoichiometry

  1️⃣ Balance the chemical equation

  2️⃣ Convert known mass to moles

  3️⃣ Use mole ratio to find moles of the other substance

  4️⃣ Convert moles to mass
• Mole-mole conversions use mole ratios from a balanced chemical equation.
• What is the primary purpose of mole-mole conversions in stoichiometry?

  Convert moles of substances
• What does a chemical equation represent?

  Chemical reaction
• What is the unit for molar mass?

  g/mol
• What is stoichiometry the study of?

  Quantitative relationships
• Stoichiometry involves the study of quantitative relationships in chemical reactions.


  True
• Steps for performing mass-mass conversions

  1️⃣ Balance the chemical equation

  2️⃣ Convert known mass to moles

  3️⃣ Use mole ratio from balanced equation

  4️⃣ Convert moles to mass
• The molar mass of MgO is 40 g/mol.
• Steps for performing mole-mole conversions

  1️⃣ Balance the chemical equation

  2️⃣ Convert known moles using mole ratios
• Mole-mole conversions use a balanced chemical equation to convert moles of one substance to moles of another substance.


  True
• Concentration is often expressed in molarity, which represents moles of solute per liter of solution