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.