Unit 3 - Topic 1 Flashcards
Explain transfer of matter and energy in an open system & give example.
Both energy and matter can transfer into surroundings
Example: Mug of coffee, pot of water
Explain transfer of matter and energy in a closed system & give example.
Only energy can be transferred - matter cannot escape.
E.g. closed coffee cup, pot covered with lid
State whether physical and chemical changes are reversible
Physical changes: generally reversible
Chemical changes: generally irreversible (only some can be reversed)
State the symbols that denotes whether a reaction is irreversible and reversible
Single forward arrow: irreversible reactions
Double arrow: reversible reaction - shows that forward and reverse reactions occur simultaneously
Define dynamic equilibrium
Occurs when reaction does not go to completion but forward and rev reaction both continue to occur - always will be some reactants and products present.
- must be closed system
- can have different reactant and product concentrations, however the concentrations remain constant over time
- the rate of fwd and rev reaction - the same
Define La Chatelier’s Principle
When a chemical system in state of equilibrium is disturbed - it will re-establish the equilibrium by partially opposing this change to reducing the effect of the change.
What happens to position of equilibrium when [substance] is increased?
In accordance to LCP - The system will shift position of equilibrium away from substance, to use up/reduce the additional substance.
Ie. if substance is a product, it will favour the reverse reaction
What happens to position of equilibrium when [substance] is decreased?
LCP means - The system will shift in a direction to produce more of the substance.
Ie. if substance is a product, it will favour the forwards reaction
What happens to position of equilibrium when temperature is increased?
According to LCP - The system will shift in direction to reduce the added heat.
- if the reaction is endothermic - will favour the forwards reaction to reduce heat (right towards products)
- if the reaction is exothermic - will favour the reverse reaction to reduce heat (left towards reactants)
What happens to position of equilibrium when temperature is decreased?
In accordance with LCP - the system will shift in direction to increase the heat - opposing this temperature change.
- if the reaction is endothermic - will favour the reverse reaction to produce heat (left towards reactants)
- if the reaction is exothermic - will favour the forwards reaction to produce heat (right towards products)
What happens to position of equilibrium when pressure is increased? (volume is decreased)
LCP means - the system will shift in direction to reduce the number of gaseous molecules, thus favouring the direction with fewer molecules
What happens to position of equilibrium when pressure is decreased? (volume is increased) (pressure and volume have inverse relationship!)
LCP means - the system will shift in direction to increase the number of gaseous molecules, thus favouring the direction with more molecules
What happens to the position of equilibrium when an inert gas is added to a system,
Inert gases are generally unreactive. As they do not react with the other substances, it does not impact concentration and thus there is no change to equilibrium position.
What happens to the position of equilibrium when a catalyst is added?
Simultaneously increases the rate of both reactions, thus achieving equilibrium faster, however there is no effect on the position of equilibrium.
How is a concentration change depicted on a graph?
Sharp increase/decrease in changed molecule, and gradual change in other molecules.
How is a temperature change depicted on a graph?
Gradual increase/decrease for all molecules
How is a pressure change depicted on a graph?
Sharp increase/decrease for all molecules
Define the equilibrium constant and the formula
Denoted by Kc
Kc = [products]/[reactants] (at equilibrium)
any coefficient of a molecule becomes a power
What is the chemical difference between acids and bases
Acids are proton (H+) donors
Bases are proton (H+) receivers
State the pH range of acids and bases, and the pH range of strong acids and bases
Acid pH < 7
Base pH > 7
Strong acid pH < 3
Strong base pH >12
Differentiate between monoprotic and polyprotic acids and give examples
Monoprotic acids: can donate 1 proton only
e.g. HCl, Hf, HNO3, Ch3COOH
Polyprotic acids: can donate multiple protons (ie. diprotic can donate 2, triprotic can donate 3)
e.g. H2SO4, H3PO4
These donations occur in stages - the first stage dissociates to greater extent than second stage
List the strong acids (name)
Hydrochloric acid, sulfuric acid, nitric acid
List the strong acids (formula)
HCl, H2SO4, HNO3
List the weak acids (name)
Ethanoic acid/acetic acid, carbonic acid, phosphoric acid
List the weak acids (formula)
CH3COOH, H2CO3, H3PO4
List the strong bases (name)
Sodium hydroxide, potassium hydroxide, calcium hydroxide
List the strong bases (formula)
NaOH, KOH, Ca(OH)2
List the weak bases (name)
Ammonia
List the weak base (formula)
NH3
