Balancing Chemical Equations Atoms can’t be created or destroyed in an ordinary reaction: All the atoms we start with we must end up with A balanced equation has the same number of each element on both sides of the equation.

Rules for balancing: Assemble the correct formulas for all the reactants and products, use + and → Count the number of atoms of each type appearing on both sides Balance the elements one at a time by adding coefficients where needed (the numbers in front) - save balancing the H and O until LAST! 4) Check to make sure it is balanced.

Never Never change a subscript to balance an equation. If you change the formula you are describing a different reaction. H2O is a different compound than H2O2 Never put a coefficient in the middle of a formula 2NaCl is okay, but Na2Cl is not.

2 Mg + O2 2 MgO +

2 Mg + O2 2 MgO +

(NH4)2Cr2O7 Cr2O3 + N2 + H2O Reactants Products N Cr H O

Practice Balancing Examples _AgNO3 + _Cu ® _Cu(NO3)2 + _Ag _Mg + _N2 ® _Mg3N2 _P + _O2 ® _P4O10 _Na + _H2O ® _H2 + _NaOH _CH4 + _O2 ® _CO2 + _H2O

Practice Balancing Examples 2AgNO3 + 1Cu ® 1Cu(NO3)2 + 2Ag 3Mg + 1N2 ® 1Mg3N2 4P + 5O2 ® 1P4O10 2Na + 2H2O ® 1H2 + 2NaOH _CH4 + 2O2 ® _CO2 + 2H2O

__Ag2CO3 __Ag2O + __CO + __O2 __NaClO4 + __CuSO4  __Na2SO4 + __ Cu(ClO4)2 __Ga + ___I2  ___Ga I3 __Cr2O3  __ CrO + __O2 ___Sn + __Ag2 SO4  __ Sn(SO4)2 + __ Ag

_1Ag2CO3 1 Ag2O + _1_CO + ½ O2 OR 2 2 2 1 _2NaClO4 + _1CuSO4  _1Na2SO4 + _1 Cu(ClO4)2 _2Ga + __3I2  __2Ga I3 _2Cr2O3  _4 CrO + _1O2 _1_Sn + _2Ag2 SO4  1 Sn(SO4)2 + _4_ Ag