Balanced Chemical Equations

• What is the purpose of chemical symbols and formulae in chemistry?

  Chemists use them to represent elements and compounds.
• What do word equations and balanced chemical equations represent?

  They represent the changes that happen in chemical reactions.
• What is a balanced chemical equation?

  • A chemical equation using symbols and formulae of reactants and products
  • Shows equal number of units of each element on both sides of the arrow
• What is a reactant in a chemical reaction?

  A substance that reacts with another substance to form products.
• What is a product in a chemical reaction?

  A substance formed in a chemical reaction.
• What are state symbols in chemical equations?

  • Symbols indicating the physical state of a substance
  • (s) for solid, (l) for liquid, (g) for gas, (aq) for aqueous solution
• What does the state symbol (aq) represent?

  An aqueous solution formed when a substance dissolves in water.
• Why are state symbols useful in chemical equations?

  They show the physical state of a substance.
• What does the law of conservation of mass state?

  The total mass of reactants equals the total mass of products in a reaction.
• What does the conservation of mass imply about atoms during a chemical reaction?

  No atoms are lost or made during a chemical reaction.
• How can chemical reactions be represented by symbol equations?

  • By ensuring the same number of atoms of each element on both sides
  • By adding numbers to the left of one or more formulae to balance the equation
• How do you balance the equation for the reaction between nitrogen and hydrogen?

  By adjusting coefficients to ensure equal numbers of each atom on both sides.
• In the equation \(N_2 + H_2 \rightarrow NH_3\), how many nitrogen atoms are on the left side?

  There are two nitrogen atoms on the left side.
• What should you do if there are unequal numbers of atoms on both sides of a chemical equation?

  Add balancing numbers to the left of the formulae.
• What is the final balanced equation for the reaction between nitrogen and hydrogen?

  N_2(g) + 3H_2(g) → 2NH_3(g)
• What is a key fact about balanced chemical equations?

  • They only show formulae, not names
  • A balancing number multiplies all the atoms in the substance next to it