Unit 3: Balancing Equations Section 2: Balancing Techniques

Counting Atoms To balance equations, you must be able to count the atoms given Subscripts Parentheses Coefficients

Subscripts Small-sized numbers that are written after the element symbol and placed slightly lower H2O 2- H atoms 1- O atom NH4NO3 2- N atoms 4- H atoms 3- O atoms

Parentheses Used to group elements together Ca(NO3)2 Mg3(PO4)2 1- Ca atom 2- N atoms 6- O atoms Mg3(PO4)2 3- Mg atoms 2- P atoms 8- O atoms

Coefficients Number placed in front of the formula, to multiply the entire formula 3Ca(NO3)2 3- Ca atoms 6- N atoms 18- O atoms 5Mg(C2H3O2)2 5- Mg atoms 20- C atoms 30- H atoms 20- O atoms

Practice Time Answer questions 1-6!

Balanced Equation A chemist’s recipe Tells what reactants and its amount to mix together Tells what the end product(s) and its amount will be

Balancing Rules Can only add coefficients to balance, not subscripts Never try to balance the number of oxygen atoms first, start with another element Coefficients must be whole numbers

Balancing Unbalanced equation: Balanced equation: CH4 + O2  CO2 + H2O C-1 C-1 H-4 H-2 O-2 O-3 Balanced equation: CH4 + 2O2  CO2 + 2H2O

Balancing Unbalanced equation: Balanced equation: Al2O3  Al + O2 Al-2 Al-1 O-3 O-2 Balanced equation: 2Al2O3  4Al + 3O2

Work on the practice problems! Practice Time Work on the practice problems!