CHEMICAL FORMULAS & EQUATIONS

CHEMICAL FORMULA Everyone knows at least one chemical formula H2O This represents the presence of 2 Hydrogens and one oxygen in every molecule of water Any number below the line applies to the element in front of it

CHEMICAL FORMULAS & RATIOS Molecules have very specific numbers of atoms present. If I change water to H2O2 it becomes peroxide Salts are represented by the simplest ratio of elements, i.e table salt, NaCl or Magnesium Chloride, MgCl2

CONSERVATION OF MASS Mass can be neither created nor destroyed In a chemical reaction reactants (left side of the equation)are disassembled and rearranged in to products (right side of the equation) Mass is conserved

CHEMICAL EQUATIONS A chemical equation is like a mathematical equation C2H6 + O2 →CO2 + H2O REACTANTS PRODUCTS The number of atoms on the reactant side must equal the number of atoms on the product side.

BALANCING A CHEMICAL EQUATION C2H6 + O2 →CO2 + H2O 2 C 1C 6 H 2 H 2 O 3 O We can’t change the number below the line so what can we do?

BALANCING A CHEMICAL EQUATION When you add a number in front of a molecule it applies to the whole molecule. C2H6 + 31/2 O2 → 2 CO2 + 3 H2O Whole numbers are preferable but in VCE chemistry half numbers are allowable 2 C2H6 + 7 O2 → 4 CO2 + 6 H2O

FINAL STEP To complete your chemical equation add states of matter 2C2H6 (g)+ 7O2 (g)→ 4CO2 (g) + 6H2O (g) (g) = gas (aq) = aqueous (l) = liquid (s) = solid

Can you balance these equations? Mg(s) + O2(g) → MgO(s) H2SO4(aq) + NaOH(aq) → Na2SO4(aq) + H20(l)