Chemical Reactions

Balancing Chemical Equations

1. Both sides must contain the same number of each type of atom 2. You can change the coefficients (the number in front of each molecule) but not the subscripts in balancing 3. For complicate reactions it may help to make a table of reactants and products

Types of Chemical Reactions

1. Synthesis (or combination) 2. Decomposition or balancing 3. Single Replacement 4. Double Replacement

Are the respective coefficients of the balanced equation: CO2 + H2O → C6H12O6 + O2

6, 6, 1, 6

Single Replacement

Al + HCl → AlCl3 + H2

BaCl2 + Na2SO4 →

BaSO4 + 2NaCl

2HgO --> 2Hg + O2

Decomposition

Chemical Equations

During a chemical reaction, one or more new compounds are formed as a result of the rearrangement of atoms.

As a group they have an oxidation number that can be determined by the molecule adding to 0

Ex HNO3 H is +1 so the NO3 must be -1.

What are the oxidation numbers for Fe and Cl in the compound FeCl3

Fe +3 Cl -1

non transition elements

For non transition elements the column indicates the oxidation number. Col 1,2,3 have +1, +2, +3 while columns 5,6,7 have -3,-2,-1

Double Replacement

NaCl + H2SO4 → Na2SO4 + HCl

SO3 + H2O --> H2SO4

Synthesis

Is the following chemical equation balanced? 1 CH4 + 2O2 → 2 H2O+1 CO2

Yes, because the same number of each of the atoms appear before and after.

Radicals

collections of atoms that act as a group in a molecule. SO4 (sulfate), NO3 (nitrate), PO4 (phosphate).

Use of Periodic Table to determine oxidation numbers

non transition elements transition elements

parts in a chemical reaction

reactants → products

Oxidation Numbers

represent the number of electrons donated (positive) or accepted (negative) For any molecule the total must be zero

transition elements

transition elements must be determined by the molecule totaling 0.