U2 S1 L4
Writing Bronsted-Lowry equations:
predictions.
P 562
Upon completion of this lesson, you should be able to:
• predict the most likely acid-base reaction using a table of
relative acid-base strengths
• predict whether or not an acid-base reaction goes to
completion and use appropriate symbols to represent
equilibrium and non-equilibrium acid-base systems
• predict whether reactants or products are favoured in an
acid-base equilibrium
• write total ionic and net ionic equations specific to acidbase reactions
Net ionic review:
•
net ionic equations
–
display only the species that actually undergo some change in bonding. (recall
that spectator ions cross out)
Ex: silver nitrate reacts with potassium chloride
1.
Total non-ionic equation:
2.
Total ionic equation:
3.
Net ionic equation:
Steps for writing Net ionic equations for Bronsted Lowry Acid/Base reactions
1.
List all species present.
•
•
•
•
Ionic compounds 100% dissociated
Strong acids (100% ionized)
Weak acid (written in full)
Water is always present
2.
Identify strongest acids/bases (use table)
3.
Write the acid / base reaction using the stronger acid and stronger base.
4.
Determine the nature of the reaction:
–
Stoichiometric (100% single arrow) reactions occur between:
•
hydronium and bases stronger than nitrite in the acid-base table.
•
hydroxide and acids stronger than hypochlorous acid in the acid-base
table.
–
Non-stoichiometric (< 100% double arrow) reactions occur between:
•
weak acids and weak bases.
•
hydronium and bases weaker than fluoride.
•
hydroxide and acids weaker than hydrogen sulfite.
5. Determine the position of equilibrium.
•
–
Consider the acid / conjugate acids strengths
if the acid is stronger than the conjugate acid, the equilibrium lies to
the right: products are favoured
–
if the conjugate acid is stronger than the acid, then the equilibrium lies
to the left: reactants are favoured
1) Write an equation for the acid-base reaction between
aqueous sodium hydroxide and hydrochloric acid.
2) Write an equation for the acid-base reaction between
nitrous acid and aqueous sodium sulfite
3) Write an equation for the acid-base reaction between hydrochloric acid and
aqueous sodium sulfide
The horizontal line between nitrite and fluoride in the acid-base strength table is used to
determine whether or not this reaction is stoichiometric.
In this case S2- is a stronger base than nitride, thus stoichiometric.
4) A paste of baking soda can be used to neutralize a sodium hydroxide spill. Write an
equation for the acid-base reaction between aqueous sodium hydroxide and
aqueous sodium hydrogen carbonate
The horizontal line between hydrogen sulfite and hypochlorous acid in the acid-base
strength table is used to determine whether or not this reaction is stoichiometric.
hydrogen carbonate well below the short horizontal line , thus non- stoichiometric.
5) Oven cleaner (aqueous NaOH) is neutralized by vinegar (CH3COOH). Write
the equation for the Brønsted-Lowry acid-base reaction that should take
place.
Extra Practice:
Write equations for acid-base reactions for each pair of given
substances. You can assume that ionic compounds are aqueous.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
sodium sulfate and ammonium
sodium carbonate and acetic acid
ammonia and nitrous acid
nitric acid and rubidium hydroxide
sulfurous acid and potassium phosphate
benzoic acid and sodium hydroxide
oxalic acid and potassium hydrogen phosphate
hydrofluoric acid and ammonium acetate
carbon dioxide dissolved in water and potassium sulfide
aqueous sulfur dioxide and aqueous ammonia
sodium bicarbonate and gastric acid (HCl)
potassium hydrogen sulfate and sodium carbonate