1.4 Chemical Formulae, Equations, and Calculations

• Chemical symbols are single letters, while chemical formulae use subscripts.


  True
• The unbalanced equation for the reaction of hydrogen and oxygen to form water is H2 + O2 → H2O
• Match the chemical symbol with its element:

  H ↔️ Hydrogen

  O ↔️ Oxygen

  Na ↔️ Sodium
• Balancing chemical equations ensures the conservation of mass by making sure the number of atoms of each element is equal on both sides.

  True
• Give an example of a synthesis reaction.

  2Na + Cl₂ → 2NaCl
• An example of a decomposition reaction is 2H₂O → 2H₂ + O₂
• The mole is a unit of measurement used in chemistry to quantify the amount of a substance
• In a decomposition reaction, a single reactant breaks down into two or more products
• The reaction 2Na + 2HCl → 2NaCl + H₂ is an example of a single displacement reaction.


  True
• Match the type of reaction with its description:

  Synthesis ↔️ Two or more reactants combine to form a single product

  Decomposition ↔️ A single reactant breaks down into two or more products

  Single Displacement ↔️ One element replaces another in a compound

  Double Displacement ↔️ Two compounds exchange ions
• Chemical formulae use subscripts to indicate the number of atoms
• Steps to balance a chemical equation

  1️⃣ Write the unbalanced equation

  2️⃣ Identify the elements and count atoms

  3️⃣ Adjust the coefficients to balance atoms

  4️⃣ Check the balanced equation
• The balanced equation for the reaction of hydrogen and oxygen to form water is 2H2 + O2 → 2H2O
• Steps to balance a chemical equation

  1️⃣ Write the unbalanced equation

  2️⃣ Count the atoms of each element

  3️⃣ Adjust the coefficients

  4️⃣ Check the balanced equation
• In a synthesis reaction, two or more reactants combine to form a single product
• Match the reaction type with its description:

  Synthesis ↔️ Two reactants combine

  Decomposition ↔️ Single reactant breaks down

  Single Displacement ↔️ One element replaces another

  Double Displacement ↔️ Two compounds exchange ions
• The reaction 2Na + Cl₂ → 2NaCl is an example of a synthesis reaction.

  True
• In a single displacement reaction, one element in a compound is replaced by another element
• The reaction NaCl + AgNO₃ → NaNO₃ + AgCl is an example of a double displacement reaction.

  True
• The molar mass is the mass of one mole
• The variable 'm' in the formula $n =$$\frac{m}{M}$ represents mass
• What is the mole ratio between Na and H₂ in the reaction $2Na +$$2HCl \rightarrow 2NaCl +$$H_{2}$?


  2:1
• Chemical formulae use subscripts to indicate the number of atoms in a compound.


  True
• Steps to balance a chemical equation:

  1️⃣ Write the unbalanced equation

  2️⃣ Identify the elements and count their atoms

  3️⃣ Adjust the coefficients to balance the atoms

  4️⃣ Check that the equation is balanced
• The purpose of balancing chemical equations is to conserve both mass and atoms
• After adjusting coefficients, it is necessary to ensure the equation is balanced by checking the number of atoms of each element
• What is the balanced equation for the reaction of hydrogen and oxygen to form water?

  $2H_{2} +$$O_{2} \rightarrow 2H_{2}O$
• What is the mole used to quantify in chemistry?

  Amount of substance
• What is the first step in performing mass-to-mass conversions using mole ratios?

  Write the balanced equation
• The molar mass is the mass of one mole of a substance.


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

  Write the balanced equation ↔️ Ensures the reaction stoichiometry is correct

  Identify the mole ratio ↔️ Determines the relative amounts of reactants and products

  Convert the given mass ↔️ Uses molar mass to find moles
• What is the number of moles of H₂ produced when 0.435 moles of Na react in the equation 2Na + 2HCl → 2NaCl + H₂?

  0.218 mol
• Percentage yield compares the actual yield to the theoretical yield.

  True
• What is the percentage yield if the actual yield of H₂ is 0.3 g and the theoretical yield is 0.831 g?

  36.1%
• Steps to calculate the empirical formula

  1️⃣ Convert percentages to grams

  2️⃣ Convert grams to moles

  3️⃣ Find the simplest mole ratio

  4️⃣ Round to whole numbers
• What method is used to calculate ionic formulas from ion charges?

  Cross-multiplication
• The ionic formula for sodium chloride is NaCl.
• What do chemical symbols represent in chemistry?

  Elements in the periodic table
• Match the chemical symbol with its element:

  H ↔️ Hydrogen

  O ↔️ Oxygen

  Na ↔️ Sodium
• Balancing chemical equations ensures the conservation of mass and atoms.

  True