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Unit 3: Chemical Equations and Stoichiometry
Balancing Equations
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Balancing Equations reactants products
Remember the law of conservation of mass? When a chemical reaction occurs, no atoms are created or just destroyed – they are just rearranged amount of each element on the left side (reactants) must equal the amount of the same element on the right side (products) reactants products
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Balancing Equations – The Steps!
Write the unbalanced equation Ionic compounds: charges must add to zero Covalent compounds: use prefixes HOFBrINCl elements are diatomic when alone Example: hydrogen gas is written H2 Add phase if given: Solid = (s) Gas = (g) Liquid = (l) Aqueous (dissolved in water or solution) = (aq)
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Balancing Equations Practice #1
Write and balance the following chemical equation: Lead (IV) sulfide solid + oxygen gas lead (IV) oxide solid + sulfur dioxide gas
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Balancing Equations – The Steps!
Put coefficients in front of each substance to get the quantities on the left side = the right side Use the smallest whole number coefficients possible.
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Balancing Equations - Hints
Save “singletons” for last (elements that are not bonded with other elements) Save oxygen for last (if there are no singletons) Save hydrogen for 2nd to last
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Balancing Equations Example #1
Now let’s balance this equation… __PbS2 (s) + __O2 (g) __ PbO2 (s) + __SO2 (g)
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Balancing Equations Check-in
Write and balance the following chemical equation: iron metal + oxygen gas iron (III) oxide solid
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Balancing Equations Practice #2
Write and balance the following chemical equation: ammonium phosphate soln. + magnesium nitrate soln. ammonium nitrate soln. + magnesium phosphate solid
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