Types of Chemical Reactions

Types of Reactions

• Synthesis Reactions: Two or more substances combine to form a new compound.
  • Example: 2H2 + O2 → 2H2O
• Decomposition Reactions: A single substance breaks down into two or more substances.
  • Example: 2H2O → 2H2 + O2
• Replacement Reactions: One element replaces another element in a compound.
  • Example: Zn + CuSO4 → ZnSO4 + Cu
• Combustion Reactions: A substance reacts with oxygen to produce heat and light.
  • Example: 2CH4 + 3O2 → 2CO2 + 3H2O
• Neutralization Reactions: An acid reacts with a base to form a salt and water.
  • Example: HCl + NaOH → NaCl + H2O
• Oxidation-Reduction Reactions: One substance loses electrons (oxidized) while another substance gains electrons (reduced).
  • Example: 2Na + Cl2 → 2NaCl

Balancing Equations

• Step 1: Write the unbalanced equation: Write the reactants on the left and products on the right.
• Step 2: Count the atoms: Count the number of atoms of each element on both the reactant and product sides.
• Step 3: Balance the atoms: Add coefficients (numbers in front of formulas) to balance the number of atoms of each element.
  • Start with the elements that appear in the greatest number of formulas
  • Balance elements that appear in multiple formulas last
• Step 4: Check the equation: Verify that the number of atoms of each element is equal on both sides.
• Tips:
  • Balance elements that are combined in a formula unit (e.g. water, H2O) together
  • Don't change the subscripts (numbers in the formula) when balancing an equation

Types of Reactions

• Synthesis reactions involve the combination of two or more substances to form a new compound, such as 2H2 + O2 → 2H2O.
• Decomposition reactions involve a single substance breaking down into two or more substances, such as 2H2O → 2H2 + O2.
• Replacement reactions involve one element replacing another element in a compound, such as Zn + CuSO4 → ZnSO4 + Cu.
• Combustion reactions involve a substance reacting with oxygen to produce heat and light, such as 2CH4 + 3O2 → 2CO2 + 3H2O.
• Neutralization reactions involve an acid reacting with a base to form a salt and water, such as HCl + NaOH → NaCl + H2O.
• Oxidation-reduction reactions involve one substance losing electrons (oxidized) while another substance gains electrons (reduced), such as 2Na + Cl2 → 2NaCl.

Balancing Equations

• The first step in balancing an equation is to write the unbalanced equation, separating reactants from products.
• The second step is to count the atoms of each element on both the reactant and product sides.
• The third step is to balance the atoms by adding coefficients (numbers in front of formulas) to ensure equal numbers of atoms of each element on both sides.
• Start balancing with elements that appear in the greatest number of formulas, and balance elements that appear in multiple formulas last.
• The fourth step is to check the equation to verify that the number of atoms of each element is equal on both sides.
• Tips for balancing equations include balancing elements that are combined in a formula unit (e.g., water, H2O) together, and not changing the subscripts (numbers in the formula) when balancing an equation.