Key Area 4 Flashcards
Does a weak acid have a high or low pKa?
High
Why does adding hydrogen ions to the salt of a weak acid result in the formation of undissociated weak acid molecules?
Hydrogen ions react with negative ions in the salt
What is meant by a weak acid?
An acid that only partially dissociates into ions in aqueous solution
What is Le Chatelier’s principle?
Any change in a system at equilibrium results in a shift in equilibrium in/to the direction that minimises the change
What does a value of K that is larger than 10³ (K>10³) suggest about the equilibrium of a reaction?
The reaction is effectively complete, therefore equilibrium moves to the right hand side (towards the products)
What does a value of K that is smaller than 10-³ (K<10-³) suggest about the equilibrium of a reaction?
There is effectively no reaction (taking place), therefore the equilibrium moves to the left (towards the reactants)
What does a value of K that is between 10-³ and 10³ (10-³>K>10³) suggest about the equilibrium of a reaction?
There is significant quantities of both reactants and products, therefore there is no effect on equilibrium
What happens when K=1?
K gives no indication of the rate at which equilibrium is established
What is K unaffected by?
Catalysts and changes in concentration and pressure
What is an example of a strong acid?
Hydrochloric acid (HCl), Nitric acid (HNO³), and Sulfuric acid (H²SO⁴)
What is an example of a weak acid?
Ethanoic acid (CH³COOH)
What is an example of a strong base?
Sodium hydroxide (NaOH), and Potassium hydroxide (KOH)
What is an example of a weak base?
Ammonia (NH³)
What is the pH of a salt of a strong acid and strong base?
Equal to 7
What is the pH of a salt of a strong acid and weak base?
Smaller than 7
