Chemical Reactions and Balancing Equations

• Chemical reactions are represented by chemical equations.
• The number of atoms for each element needs to be the same on both sides of a chemical equation; this is called balancing.
• Atoms are neither created nor destroyed during a chemical reaction due to the Law of Conservation of Mass.
• The law of conservation of mass is why chemical equations need to be balanced.
• Cooking and respiration are examples of chemical reactions.
• Hair dye and auto fuel are chemical reactions that occur everyday.

Evidences of Chemical Reactions

• Color change.
• Odor change.
• Formation of gas.
• Formation of precipitate.
• Temperature change.
• Change in acidity.

Fuels

• A fuel is something that can be burned to release light and heat energy.
• Coal, oil, and gas are considered fuels.
• They are fossil fuels.
• In a physical change, matter changes form, but not its chemical identity.

Physical Changes

• Melting ice.
• Shredding paper.
• Chopping wood.
• Mixing gray and green marbles.

Chemical Changes

• A chemical reaction occurs and new products are formed.
• Burning wood.
• Mixing vinegar and baking soda.
• Fireworks.
• Rotting banana.
• Before a chemical reactions wood is a log.
• During a chemical reaction the log is burned.
• After a chemical reaction pile of ash remains.
• Prior to a physical change is a whole lemon
• During a physical change the lemon is sliced.
• After a physical change the lemon slices are present.

Chemical Reactions

• A chemical reaction is a process where one or more substances (reactants) change into one or more new substances (products).
• Using "A + B → AB" as a chemical equation, A and B are the reactants, and AB is the product. -In law of conversation of mass, the mass is always the same amount at the beginning as there are at the end
• Log (30 kg) + Fire (1 kg) → Ashes (28 kg) + Smoke (3 kg).
• Mass cannot be created or destroyed in a chemical reaction.
• In a chemical reaction, matter is neither created nor destroyed.
• Atoms cannot change their identity.
• The number of each type of atom on each side of the chemical equation must be the same.
• A chemical reaction is described by a chemical equation.
• The equation provides expression that gives the identities and quantities of the substances involved in a reaction.

Chemical Equations Show

• The starting compound(s)—the reactants—on the LEFT.
• The final compound(s)—the products—on the RIGHT.

What Is a Chemical Equation?

• A chemical equation is a written representation of a chemical reaction.
• 2H2(g) + O2(g) → 2H2O(l) is an example of a chemical equation.
• The coefficients are the numbers before the element (2H2).
• The reactants are on the left side of the reaction arrow (2H2(g) + O2(g)).
• Subscript is the number denoting how many of that elements is found within the molecule (2H2(g)).

Chemical Formula

• The state of matter of each reactant.
• The products are on the right side of the reaction arrow (2H2O(l)).
• Plus sign (+) separates more than one reactant or product.
• Separates reactants from products and indicates direction of reaction

Symbols Used in Chemical Equations

• "(s)" identifies a solid state.
• "(aq)" identifies that something that is dissolved in water.
• "(l)" identifies liquid state.
• "(g)" identifies gaseous state.

Reactants

• Carbon dioxide (CO2) and water (H2O).

Products

• Glucose (C6H12O6) and oxygen gas (O2).
• 3CO2 is an example of a chemical equation.
• "3" is the coefficient.
• "2" is the subscript.
• 3Mg(NO3)2 equation, the "3" is the coefficient and the "3" is the subscript.
• Chemical equations must be balanced so the reactants equal the products.
• The most important thing about balancing equations is that atoms of each element have to be the same on each side of the equation.

Law of Conservation of Mass

• CH4 + 2O2 → CO2 + 2H2O is an example of a balanced equation.
• When balancing chemical equations, ensure the same number of atoms of each element are present.
• N2 + O2 → N2O5 is an unbalanced equation.
• 2N2 + 5O2 → 2N2O5 is the same equation balanced.
• Fe + Cl2 --→ FeCl3 is an unbalanced equation.
• 2Fe + 3Cl2 --→2FeCl3 is the same equation balanced.
• P4O10 + H2O → H3PO4 is an unbalanced equation.
• P4O10 + 6 H2O → 4 H3PO4 is the same equation balanced.
• SiCl4 + H2O → H4SiO4 + HCl is an unbalanced equation
• SiCl4 + 4H2O → H4SiO4 + 4HCl is the same equation balanced.
• KCIO3 → KCIO4 + KCl is an unbalanced equation.
• 4KCIO3 → 3KCIO4 + KCl is the same equation balanced.
• Zn + HCl→ ZnCl2 + H2, CH4 + O2 → CO2 + H2O, Fe + NaBr FeBr3 + Na, SiCl4 + H2O → SiO2 + HCl, N2 + O2 + H2O HNO3, P4+ O2 P2O5, NaNO3 → NaNO2 + O2, C3H8 + O2 CO2 + H2O, Fe + H₂O H2 + Fe3O4, and Al + O2→ Al2O3 all must be balanced following the principles of the Law of Conservation of Mass. C6H12O6---> C + H2O is an unbalanced equation
• C6H12O6---> 6C + 6H2O is the same equation balanced. FeCl3+Fe2O3--->FeOCl is an unbalanced equation.
• FeCl3+Fe2O3---> 3FeOCI is the same equation balanced.

Types of Chemical Reactions

• Combination
• Combustion
• Single replacement.
• Decomposition.
• Double replacement.
• Combination or Synthesis Reaction: A + B → AB.
• Decomposition Reaction: A B → A + B.
• Single-replacement Reaction: A + B C → A C + B.
• Double-replacement Reaction: A B + C D → A D + C B.
• Combustion Reaction: (CxHy) + O2 → CO2 + H₂O
• Single displacement reaction, synthesis reaction, decomposition reaction, and double displacement reaction are all examples of types of chemical reactions.

Synthesis/Combination Reaction

• A reaction where two reactants combine to make a larger, more complex product "A + B → AB".
• A reaction where two or more substances (reactants) combine and form a compound (product).
• Sodium + Chlorine → Sodium chloride is an example.

Synthesis (Combination) Reaction examples

• 3 H₂ + N2 → 2 NH3
• MgO + CO₂→MgCO3
• 2 CO + O2→2 CO₂

Decomposition reaction

• A single compound is broken down into two or more products.
• AB=A+B is the expression.
• If there is the single compound "AB", it decomposes into "A + B".
• 2H₂O₂ is broken down to (2H₂O + O2) .This requires that the single compound is broken down into two or simpler products.

Decomposition Reaction Examples

• 2 Fe(OH)3→ Fe2O3 + 3 H₂O
• 2 H₂O→ 2 H₂ + O2
• 2 AgBr→ 2 Ag + Br2

Single Replacement

• A+BC→B+AC
• “A” replaces another element in a compound
• Mg +Zn(NO3)2 → Mg(NO3)2 + Zn, Mg + 2AgNO3 → Mg(NO3)2 + 2Ag, Mg + LiNO3 NR are examples of Single Replacement.

Cation Replacement Reactions

• Zn + 2HCl→ ZnCl2 + H2 is a cation replacement reaction example.

Single-Replacement Reaction Examples

• 2 K + 2 H₂O→ 2 KOH + H₂
• Mg + Cu(NO₃)₂→ Mg(NO3)2 + Cu
• Zn + 2 HCl→ ZnCl₂ + H₂

Double Replacement

• AB+CD→AD+CB is the expression for a Double Replacement reaction. The ions are exchanged to form new compounds.

Double Displacement

• AgNO3 + NaCl → AgCl + NaNO3 is an example.
• KBr + AgNO3 → KNO3+ AgBr is another example.

Double-replacement Reaction Examples

• KBr + AgNO₂→ KNO₂ + AgBr↓
• Na₂SO₄ + SrCl₂→ 2 NaCl + SrSO4↓
• HCI + NaOH→ NaCl + H₂O

Combustion

• Combustion is a reaction of an element or compound with oxygen to form an oxide and produce heat.Hydrocarbons combust with oxygen to produce carbon dioxide and water.
• CxHy + O2 → H2O + CO2
• CH4 + O2 → H2O + CO2
• C5H12 + O2 → H2O + CO2

What Is a Combustion Reaction?

• A combustion is a chemical reaction between a fuel and an oxidant produces an oxidized product.
• This is a reaction between hydrocarbon and oxygen yields carbon dioxide, water, and heat.
• Hydrocarbon + Oxygen → Carbon Dioxide + Water + Heat
• Example: CH₄(g) + 2 O2 (g) → CO2(g) + 2 H2O(g)

Combustion Reaction Examples

• C + O2 →CO₂
• C3H8 + 5 O2 →3 CO2 + 4 H₂O
• 2 CH3OH + 3 O2 →2 CO2 + 4 H₂O

Identify the Types of Chemical Reaction.

• 2 Na + Cl₂→ 2 NaCl is an example chemical equation.
• H₂CO₃ →CO₂ + H₂O example of a type of a chemical equation
• Cl₂ + Cal₂→CaCl₂+ I₂ example one of types of chemical equation .
• Na₂S + 2 HCI→ 2 NaCl + H₂S↑ is an example chemical equation.

Practicing Balancing Equation

• Balance the chemical equation and determine the type of chemical reaction.
• P + O2 → P2O5 this does not show the balanced equation .
• 4 P + 5 O2 → 2 P2O5 is balanced and classified as SYNTHESIS / COMBINATION.