U1 : Topic 5 Equilibrium Flashcards
When is a chemical reaction at equilibrium?
When the rate of the forward reaction is equal to the rate of the reverse reaction.
When a reaction mixture has reached equilibrium the composition of the reactants and products ….
Remain constant.
Increasing concentration of reactant effect?
Increase rate of forward reaction equilibrium moves to the right.
Increase concentration of product effect?
Increase the rate of reverse reaction so equilibrium moves to the left.
Increase temperature effect?
Favours endothermic reaction equilibrium moves in direction of endothermic.
Increase pressure effect?
Favours a decrease in pressure equilibrium moves to side with fewest moles of gas.
Use of catalyst effect?
No effect (reaches equilibrium. faster)
What is the constant K?
Ratio between the reactants and products.
[A], [B],[C],[D] are what?
Concentrations at equilibrium.
Can be expressed as number of moles or pressure as well as concentration.
a, b, c, and d are what?
The stoichiometric coefficients in the balanced reaction equation. The numbers in front of the formula
The concentrations of pure solids and pure liquids at equilibrium are taken as constant and given value of?
1
The equilibrium lies to the left hand side what is the value of K?
Less than 1.
If the value of K is 1 what is the position of equilibrium?
50% of each
Position of equilibrium is R.H.S what is the value of K?
Greater than 1
what factors don’t affect K?
Concentration, pressure, addition of catalyst.
When the concentration of a reactant or product is altered what happens to equilibrium?
It will adjust to counteract this change. Doing this will change the concentration of other reactants and products but ratio K will remain constant.
If you alter the pressure of the system the equilibrium will adjust the concentrations of?
Reactants and products counteracting the pressure change keeping K constant.
How does the addition of a catalyst affect K?
No affect to quantities of reactants or products. Reaches equilibrium faster.
The value of K is affected by what?
Temperature
Increasing Temperature does what to K in endothermic?
Favours endothermic reaction, so equilibrium shifts to the right increasing concentration of products, k increases and so does yield of product.
Exothermic reaction to temperature increase what happens to K?
Equilibrium shifts to left increasing concentration of reactants and k decreases yield of products also decreases.
According to Brønsted-Lowry what is the definition of an acid?
Proton donor.
According to Brønsted-Lowry what is the definition of a base?
Proton acceptor
Water is amphoteric what does this mean?
Can act as both an acid and base.
What are examples of strong acids?
Hydrochloric acid, sulfuric acid and nitric acid.
Strong acids completely what?
Dissociate into ions in aqueous solutions.
Examples of weak acids?
Ethanoic acid, carbonic acid and sulfurous acid.
Weak acids only partially what?
dissociate into ions in aqueous solution.
When carbon dioxide and other non-metal oxides dissolve in water they produce?
Acidic solutions
What does Equimolar mean?
Solutions that contain the same number of moles.
A strong acid has a ……. pH than a weak acid.
Lower.
A strong acid has a …… conductivity than a weak acid.
Higher
A Strong acid has a ………. rate of reaction with Mg than a weak acid.
faster
Compared to a weak acid a strong acid has an equal what?
Stoichiometry.
The more hydrogen ions present the lower the ….. , the higher the …… and the faster the …….
pH
Conductivity
Rate of reaction
Strong acid concentration will be equal to concentration of?
H+ ions.
Since a weak acid only partially dissociates the concentration of h+ ions will be?
Much lower than the acid.
Ka is a measure of what?
Strength of acid.
In strong acids Ka has what?
No meaning
The smaller the value of Ka the …… the acid.
Weaker.
when an acid is diluted the pH increases towards?
7
Examples of strong bases?
metal hydroxides (calcium hydroxide, sodium hydroxide)
Strong based completely…… in aqueous solutions.
dissociate into ions in aqueous solutions.
what are examples of weak bases?
Ammonia and amines.
Weak bases only what in aqueous solutions?
Partially dissociate into ions.
Strong bases will have ……. pH, …….. conductivity and …….. rate of reaction than weak bases.
Higher
Higher
Faster
When an alkali is diluted the pH does what?
Decreases towards 7.
To calculate the pH of strong alkali you need to do what first?
Work out concentration of hydrations using Kw.
What is formed during a neutralisation reaction?
Salt
A strong acid and a strong base produce a salt with what pH?
Neutral
A strong acid and a weak base produce a salt with what pH?
less than 7 (acidic)
A weak acid and a strong base produce a salt with what pH?
greater than 7 (alkaline)
Using appropriate equilibrium the change of concentrations of what can be explained?
H3O+ and OH- ions of salt solutions.
What is a buffer solution?
One which the pH remains approximately constant when small volumes of acid, base or water are added.
A buffer can be … or ….
Acidic or basic.
What is an acidic buffer?
Solution of weak acid and a salt of weak acid.
How does an acid buffer work?
The weak acid Provides hydrogen ions when they are removed by the addition of a small amount of base. The salt provides conjugate base which can absorb excess hydrogen ions produced by addition of small amount of acid.
What is a basic buffer?
Consists of solution of weak base and one of its salts.
How does a basic buffer work?
The weak base removes excess hydrogen ions and the conjugate acid provided by the salt supplies hydrogen ions when these are removed.
What are indicators used for?
To show the end point of a titration.
What are indicators?
Weak acids.
Colour of the indicator must be distinctly different from….
The conjugate base.
