Reactants: Zn + IReactants: Zn + I22 Product: ZnIProduct: ZnI22

used to convey as much info. as possible about what happens in a chemical reaction

Word Equations write out what chemicals are reacting

hydrogen peroxide → water + oxygen hydrogen + oxygen → water

Chemical Equations show the chemical formulas of the chemicals

reacting H2O2 (aq) → H2O(l) + O2(g) H2(g) + O2(g) → H2O (l) (s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous

solution (dissolved in water) the above are often referred to as skeletal equations

because they are not mathematically balanced

chemical equations show the conversion of reactants (the molecules shown on the left of the arrow) into products (the molecules shown on the right of the arrow).

a (+) sign separates molecules on the same side

the arrow is read as “yields” example

C + O2 CO2

this reads “carbon plus oxygen react to yield carbon dioxide”

a catalyst is a substance that speeds up the reaction but is not used up in the reaction

H2(g) + O2(g) H2O (l) this is written small over the yield arrow

MnO4

each side of the equation must have the same number of atoms of each element

bicycle example frame + wheel + handlebar + pedal → bike frame + 2 wheel + handlebar + 2 pedal → bike

tricycle example frame + wheels + handlebar + tire → tricycle frame + 3 wheel + handlebar + 3 tire → tricycle

when balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction

coefficients represent the number of atoms (or moles) of that compound

sometimes easier if you balance O and H at the end

you may NOTNOT change the subscripts changing the subscripts changes the

compound ex: H2O (water) cannot be changed into H2O2

(hydrogen peroxide) in order to help you balance the equation

H2(g) + O2(g) → H2O (l)

subscripts tell you how many atoms of a particular element are in a compound.

coefficients tells you about the quantity, or number, of molecules of the compound

this is NOT balanced

1. A solution of sodium iodide is added to a solution of potassium nitrate yields a potassium iodide precipitate and a sodium nitrate solution.

NaI (aq) + KNO3 (aq) KI (s) + NaNO3 (aq)already balanced

2. Magnesium metal burns in oxygen gas with a bright white light to make a white powder called magnesium oxide.

Mg (s) + O2 (g) MgO (s) + heat

2Mg (s) + O2 (g) 2MgO (s) + heat

3. Gaseous hydrogen (dihydride) and gaseous oxygen (dioxide) react explosively to form water vapor.

H2 (g) + O2 (g) H2O (g) + heat

2H2(g) + O2(g) 2H2O (g) + heat

___ Al(s) + ___ Br___ Al(s) + ___ Br22(l) ---> ___ Al(l) ---> ___ Al22BrBr66(s)(s)2 3

?

Al(s) + O2(g) Al2O3(s) 4Al(s) + 3O2(g) 2Al2O3(s)

NaCl (aq) + AgNO3 (aq) AgCl (s) + NaNO3 (aq) balanced

Na2SiO3 + HF H2SiF6 + NaF + H2O Na2SiO3 + 8HF H2SiF6 + 2NaF + 3H2O