MODULE 1 Flashcards
What is a limiting reagent
- The reactant which is not produced in excess
- The reaction finishes when the limiting reagent runs out
What equation is used to work out grams of substance B when given grams of substance A
- Mass to moles of substance A
- use coefficients
Then moles to mass of substance B
How to work out limiting reagents
- Calculate moles of both reactants
- work out which gives the smallest amount of product
- Minus the moles limiting reagent from other reagent
Then work out the mass of the non limiting reagent remaining in excess
What is a strong electrolyte
A solute that completely dissociates to give ions in solution
- the reactants fully turn to ions
What is a weak electrolyte
A solute that incompletely dissociates to give ions in solution
- some reactants dissolve to ions but a lot form molecules
What happens to the density of water as it melts
Becomes more dense
- water molecules spread out when frozen
Hydrogen bonding means that water…. And why ?
- has high boiling and melting points
- retains heat for a long period of time
Because a lot of heat energy is needed to break the hydrogen bonds, energy is released as the bonds form again making it retain heat
What is Kc
Equilibrium constant
- the ratio of products to reactants at equilibrium
What is Q
The ratio of reactants to products at any given time of the reaction
If Q is less than K what will happen in the reaction in terms of reactants and products
Reactants will be converted to products until equilibrium is reached
If Q is greater than K what will happen in the reaction in terms of reactants and products
products will be converted to reactants until equilibrium is reached
When calculating K, what values must you be sure you use?
Concentrations at EQUILIBRIUM
- use an ICE table if they are not at equilibrium
What will happen to the reaction if more reactants are added?
The forward reaction will increase, the equilibrium position will move to the right
- in attempt to make more products, bringing the reaction back to equilibrium
What will happen to the reaction is more products are added?
The rate of the backwards reaction will increase, equilibrium position will move to the left
- in attempt to make more reactants and bring the reaction back to equilibrium
- remember K does not change
What is a saturated solution
The maximum amount of solute dissolved in a particular volume of solvent
How to calculate Ksp
sxs
Will a precipitate form is Qsp is less than Ksp
No precipitate will form
Will a precipitate form if Qsp is greater than Ksp
A precipitate will occur
Will the presence of a common ion decrease or increase the solubility of an ionic solid
It will decrease the solubility
- to solve set up an ICE table
Brønsted-Lowry definition of an acid
Proton donor
Brønsted-Lowry definition of a base
Proton acceptor
How many electrons do conjugate acid base pairs differ by
Differ by one electron
- the acid will have one more electron than the conjugate base
The smaller the Ka or Kb, the ……….. the acid or base
The smaller the Ka or Kb, the weaker the acid or base
The smaller the pKa or pKb, the ……… the acid or base
The smaller the pKa or pKb, the stronger the acid or base
What is a buffer solution
Made from a weak acid and a conjugate base, both at a reasonable concentration
A buffer solution will …..
- will maintain a reasonably constant pH when significant amounts of OH- or H+ ions are added
- pH of a buffer is also unaffected by reasonable dilution of the solution
What is buffer capacity
When the reaction goes to completion, meaning eventually the weak acid or its conjugate base will be used up and will no longer be a buffer solution
What occurs at the half equivalence point on a titration curve
HA and A- are equal
pH = pKa
Half equivalence point = perfect buffer
What is the equivalence point on a titration curve
All A-
What is a diprotic acid
An acid that has two protons it can donate
- will do so one at a time
At which point on a titration curve of an amino acid can a zwitterion be found
At the equivalence point
How many atoms are there in one mole
6.022x10 to power of 23
How to convert pKa into Ka
Ka = 10 to the power of negative pKa
In a saturated solution does Qsp = Ksp
Yes
How to work out the solubility of something when given the concentration of a common ion
Ksp = s(conc of common ion)
- if conc is greater than s you can ignore the second s and just use equation above
- do Ksp divided by conc of common ion to find s
How to calculate pOH
- log (OH-)
How to work out pH when given concentration of a base
Work out pOH
- log (OH-)
Then do 14 - the answer you got to get pH
More than 1 pH unit above pKa, what can be said about the molecules in an ionisable functional group
90% of molecules are deprotonated
More than 1 unit below pKa, what can be said about the molecules in an ionisable functional group
90% of molecules are protonated
Are polar molecules hydrophilic or hydrophobic
Hydrophilic - water loving
Do alcohols ionise
No
What is ionisation state influence by
- the pH of the aqueous environment
- the fundamental physical property - i.e the pKa
What is ionisation status
How easy it is to ionise
