Balancing Chemical Equations and Types of Chemical Reactions

Balancing Chemical Equations and Types of Chemical Reactions

Objectives • I can compare and contrast different types of chemical reactions. • I can define and identify a balanced chemical equation. • I can balance simple chemical equations.

Parts of a Chemical Reaction Cu (s) + 2 AgNO3 (aq) → Cu(NO3)2 (aq) + 2 Ag (s) Reactants Products Letters in parentheses show the state of matter. Coefficients (numbers) in front of a chemical formula show “how many.” The arrow separates the reactants and products.

Balancing a Chemical Reaction Equation • Atoms are not createdor destroyedduring a chemical reaction. • Scientist know that there must be the samenumber of atoms on each sideof the arrow.

Is it balanced? __Cu + __ AgNO3 → __Cu(NO3)2 + __ Ag Cu = Cu = Ag = Ag = NO3 = NO3 =

Balancing a Chemical Reaction Equation • To balance the chemical equation, you must add coefficientsto the different parts of the equation. Cu (s) + 2 AgNO3 (aq) → Cu(NO3)2 (aq) + 2 Ag (s)

Steps for Balancing Chemical Reaction Equations • Determine number of atoms for each element for the reactants and products separately. • Try to add coefficients to the equation to get the same number of atoms on each side. • Note: Coefficients multiply the atoms in the compound. Keep the compound formulas the same. Do not change subscripts. • Hint: Balance anything that is not hydrogen or oxygen first. Then balance hydrogen. Balance oxygen last.

+ H2 O2  H2O (g) (g) (l) O O O H H H H H H O H H Law of Conservation of Mass • Matter cannot be created or destroyed in a chemical reaction • The number of atoms on the reactant side must equal the atoms of the products Unbalanced! Balanced!

Balanced Chemical Equations • A chemical equation is “balanced” when there are the same number of atoms of each element on both sides of the arrow. NaHCO3 (s) + HC2H3O2 (aq) èNaC2H3O2 (aq) + CO2 (g) + H2O (l) Is it balanced?

Is it balanced? Practice • Determine the number of atoms of each element in the reactants and products. Then, state whether the equation is balanced. • P4 + O2 → P2O5 • C3H8 + O2 → CO2 + H2O • Ca2Si + Cl2 → CaCl2 + SiCl4 • Si + CO2 → SiC + SiO2 Not balanced. Not balanced. Not balanced. Not balanced.

coefficient + H2 O2  H2O (g) (g) (l) Balancing Equations 2 2 • Only the coefficients can be changed! H = O = 2 4 H = O = 2 4 2 1 2

Balancing Tips • Always balance non-Oxygen’s & Hydrogen’s first (ex. Chlorine) • Then balance Hydrogens • Balance Oxygens Last

Balancing Practice! P4 + O2 → P2O5 P4 + 5 O2 → 2 P2O5 Ca2Si + Cl2 → CaCl2 + SiCl4 Ca2Si + 4 Cl2 → 2 CaCl2 + SiCl4 Si + CO2 → SiC + SiO2 2 Si + CO2 → SiC + SiO2 C3H8 + O2 → CO2 + H2O C3H8 + 5 O2 → 3 CO2 + 4 H2O

Overview of Major Chemical Reaction Types • Synthesis • Decomposition • Single-Replacement • Double-Replacement • Combustion

+ 2H2 O2  2H2O (g) (g) (l) H H O O H H H H H H 1. Synthesis Reactions • Two substances combine to make one • Synthesismeans “to make” O O

A + B  AB SYNTHESIS Na + Cl2 NaCl

NH3 (l) N2 + H2  (g) (g) 2. Decomposition Reactions • One substance breaks down into 2 • Decompositionmeans “to break down” or “decay” H H H H N N H H

AB  A + B Decomposition NaCl  Na + Cl2

one element replaces another in a compound 3. SINGLE REPLACEMENT AB + C  AC + B

Single Replacement Reaction

Single Replacement AB + C  AC + B or CB + A NaBr + Cl2 NaCl + Br2

4. DOUBLE REPLACEMENT Both elements in two compounds switch places AB + CD  AD + CB

Double Replacement NaBr + Pb2S3 Na2S + PbBr3 K2SO4 + Ba(OH)2 KOH + BaSO4

CH4 C2H4 + + O2 O2 CO2 CO2 + + H2O H2O   C6H12O6 + O2 CO2 + H2O  5. Combustion Reactions • A hydrocarbon reacts with oxygen gas to produce carbon dioxide and water vapor • Combustionmeans to “burn in oxygen”

Balancing Chemical Equations and Types of Chemical Reactions