1.7 - Simple Equilibria and Acid-Base Titrations Flashcards
(31 cards)
What is a reversible reaction?
One that can go in either direction depending on the conditions.
What is a dynamic equilibrium?
When the foward and reverse reactions occur at the same rate.
What is Le Chatelier’s principle?
If a system at equilibrium is subjected to a change then the position of equilibrium will shift to minimise that change.
What happens when the conc of a reactant is increased?
The position of equilibrium shifts to the right and more products are formed.
What does the pressure of a gas depend on?
The number of molecules in a given gas.
The greater the number of molecules, the greater the number of collisions per unit time, therefore the greater the pressure of gas.
What does high pressure mean on an equilibrium system?
high pressure = higher amount of moles on one side
Increasing the pressure moves the position of the equilibrium to whichever side of the equation has fewer gas molecules.
What is meant by ‘endothermic’?
Absorbing heat from surroundings (positive)
What is meant by ‘exothermic’?
Gives out heat to surroundings (negative)
What reaction is it if enthalpy change is positive?
The foward reaction is endothermic
What reaction is it if enthalpy change is negative?
The foward reaction is exothermic
What do catalysts do?
Speeds up a chemical reaction by lowering the activation energy of the reaction. Does not effect the position of the equilibrium, but equilibrium is reached faster.
How does a catalyst effect a reversible reaction?
A catalyst will increase the rate of the foward reaction and backward reaction to the same extent.
What is an equilibrium constant?
The position of equilibrium in a reversible reaction may be described in precise terms by combining the equilibrium concentrations to give a value.
GIven the symbol Kc (where c indicates ratio for concentration)
What is the equation for equilibrium constant?
aA + bB = cC + dD
Kc = (C)c(D)d/(A)a(B)b
Kc = products/reactants
Conc is raised to number of moles in equation.
Units should be moldm-3
What is an acid in terms of protons?
Acids are proton (H+) donors
What is a base in terms of protons?
Bases are proton (H+) acceptors
What is the process of dissociating?
Acids donating H+ ions in an aqueous solution.
Name 4 common acids.
Hydrochloric acid HCl
Sulphuric acid H2SO4
Nitric acid HNO3
Ethanoic acid CH3COOH
Name 4 common bases.
Magnesium oxide MgO
Sodium hydroxide NaOH
Calcium oxide CaO
Ammonia NH3
What is meant by a concentrated acid?
A concentrated acid consists of a large quantity of acid and a small quantity of water.
What is meant by a dilute concentrated acid?
A dilute acid contains a large quantity of water and a small quantity of acid.
How can you measure the acidity of a solution?
Measured by the concentration of aqueous hydrogen ions.
What is the equation for pH?
pH = -log10 (H+)
(where H+ is concentration in mol dm-3)
(the negative sign is pH decreasing as H+ increases, if concentration is greater than 10-7 mol dm-3, the pH is less than 7)
Where are acids on the pH scale?
0-6 red, orange, yellow
