Acids and Bases

Question 1

what the fuck does the motherfucking, you know, fucken Brønsted-Lowry theory do (prolly fucken jack shit but whatever)

Answer 1

explains the acid-base behaviour in terms of a proton transfer reaction where bases are proton-acceptors aand acids are proton-donors

Question 2

what notion does this intorduce

Answer 2

that acid-base behaviour is relative and circumstantial, thus some substances are amphiprotic/amphoteric (can act as base or acid) depending on species they are interacting with.

Question 3

what kind of reactions are all Brønsted-Lowry reactions

Answer 3

reversible reactions, acknowledge that a substance can’t act as acid without another substance acting as a base.

Question 4

what happens when an acid loses a proton in a proton transfer reaction

Answer 4

it forms what is know as a conjugate base, while the base accepting a proton forms a conjugate acid. conjugate acid-base pair differ on ly by one proton.

Question 5

what does the arrhenius theory of acids and bases state

Answer 5

acids ionise in solutions to produce hydrogen ions while bases dissociate in solution to produce hydroxide ions.

Question 6

why is Arrhenius theory limited

Answer 6

it only applies to acid-base behaviour in aqueous solution (solvent is needed), and also doesn’t predict the basic nature of carbonates, oxides and salts that don’t contain hydroxide

Question 7

what are monoprotic acids

Answer 7

(note acids can be classified as being monoprotic or polyprotic) they can dnate a single proton per acid molecule in a transfer reaction,

Question 8

what are polyprotic acids

Answer 8

can donate more than one proton per acid molecule

Question 9

what is a conjugate base

Answer 9

A conjugate acid is formed when a proton is added to a base, and a conjugate base is formed when a proton is removed from an acid

Question 10

why is coniugate base of polyprotic acid different

Answer 10

usually is less acidic than the orginal acid ( as shown bny their individual acid constants) this is explained as the acid becomes less likely to donate positive charge (H+) as molecule becomes increasingly negative, so it becomes less.

Question 11

how is the strength of an acid determined

Answer 11

by the extent to which it ionises (via proton donation).

Question 12

what is the acid dissociation constant (Ka)

Answer 12

as proton-transfer reactions are technqically equilibrium processs, a constant can be assigned to every reaction to quantify the extent to which the reaction proceeds, which can aid in measuring acid strength

Question 13

write the acid dissociation constant (Ka)

Answer 13

seek page 9

Question 14

what if Ka is large (>1)

Answer 14

then the aiced can considered strong as it ionises to a large extent

Question 15

what if Ka is small (<1)

Answer 15

then acid can be considered weak, as few acid molecules ionise (most remain in their molecular form)

Question 16

what should be kept in mind when using the acid dissociation constant (Ka)

Answer 16

water has a fixed concentration and as such is not included in the expression

and the strong the stronger acid is, weaker its conjugate base, as conjugate base is less likely to accept a proton because acid resits reformation.

Question 17

what is the conjugate base of a weak acid known as

Answer 17

a strong base, sicne acid mostly remains in molecular form, hence conjugate base is more likely to accept a proton to reform the acid molecule.

Question 18

what is salt

Answer 18

an ionic compound that is formed in the reaction between an acid and base

Question 19

how can salt be classified

Answer 19

acidic, basic, or netural, based on way in which anin and/or cantion interacts with water since ionic compounds undergo hydrolysis reactions

Question 20

when salt classified as acidic

Answer 20

if anion/cation produces hydronium ions when reacting water, the compound is classed as acidic, as it produces a acidic solution

Question 21

when salt classified as neutral

Answer 21

if anion/cation produces hydroxide ions when reacting water, the compound is classed as basic, as it produces a basic solution

Question 22

when salt classified as basic

Answer 22

sometimes a salt has both acidic and basic ions, in this case it can be neutral or the “stronger” ion determines its properties. the properties of the salt can affect the properties of the entire solution.

Question 23

what are buffers

Answer 23

solutions that resist change in pH (within a certain range) when they have acids or bases added to them.

Question 24

what kind of pair are buffers generally

Answer 24

generally a weak acid-base conjugate pair this works becasue the pair can exist together in a solution without neutralising each other, but still neutralise any added acid or base

Question 25

what does le chateliers principle do

Answer 25

as the buffer system operates under a reversible equilibiurm reaction, the bahaviour of the system can be predicted by this

Question 26

what happens when acid or base is added to the buffer

Answer 26

equilibrium shifts t favour the reaction that consumes the added acid or base.

Question 27

what does the addition of an acid or a base do to a system

Answer 27

the addition of acid or base to system can also neutralise one of the conjugate pair species in which base equilibrium shifts to favour the reaction that produces more of this species, in both instances changes to pH are minimal.

Question 28

what is the buffer capacity

Answer 28

amount of acid or base that can be added to buffer system without significant change to pH

Question 29

higher buffer capacities

Answer 29

solution should have high concentratins of the acid-base conjugate pair, and similar concentreations or the two species making up the conjugate pair.

Question 30

explain waters self-ionisation

Answer 30

despite waters covalent molecular strucutre, it can do this, where 2 water molecules form hydronium and hydroxide ins via a proton transfer reaction.

Question 31

explain the autoionisation constant (Kw)

Answer 31

this reversbile equilibrium reaction favours formation of water molecules and hydronium and hydroxide ions have extremely small concentrations of 1.0 x 10^-7 mol^-1 at 25 C. As this reaction is in a state of equilibrium, it can be assineed the autoionisation constant (Kw)

Question 32

when is water neutral

Answer 32

if the concentration of hydrogen and hydroxide ions are equal than the water is said to be neutral.

Question 33

explain the 1.0 x 10^-7 expression of concentrations of hydronium and hydroxide ions in water.

Answer 33

in neutral water the concentraiton of hydronium ions and hydroxide ions is 1.0 x 10^-7. this expression shows that concentrations of hydrogen ions and hydroxide ions are inversely related.

Question 34

explain how the autoionisation constant varies with different temperature.

Answer 34

since its an endothermic process, increase in temp. favours formation of the products, hence increasing the concentration of hydronium and hydroxide ions in solution.

Question 35

what makes a solution neutral

Answer 35

not one that has a pH of 7, important to remember this. for a solution to be neutral, it must have equal concentrations of hydroxide and hydronium.

Question 36

what is a solutions acidity based on

Answer 36

hydrogen ion concentration, this can be used to determine pH as pH is a logarithmic function of hydrogen ion concentration. pH = - log_10[H+]

Question 37

what are indicators

Answer 37

they're weak conjugate acid-base pairs used in acid-base reactions because their colour is pH dependant.they work using le chateliers principle cause they produce an equilibrium system in which the weak acid/base is a different colour to conjugate base/acid.

Question 38

what does the addition of a base or an acid do to the concentrations of the conjugate pair

Answer 38

addition of acid or base changes the concentrations of the conjugate pair relative to one another, which cause the solution to change colour.

Question 39

what are titrations

Answer 39

a form of quantitative analysis, an analytical procedure involving an acid-base reaction

Question 40

what is the point of titrations

Answer 40

to determine the concentration of a particular solution by reacting it (acid/base) with a solution of accurately know concentration.

Question 41

what is a standard solution

Answer 41

this is the solution of accurately known concentration

Question 42

what is a 'unknown' solution

Answer 42

this is the solution whose concentration you are trying to determine

Question 43

what is the equivalence point in a titration

Answer 43

is the point at which the species involved in the reaction exist in the stoichiometric ratios indicated in the balanced chemical equation for the reaction. (Where all the acid/base in the aliquot has been neutralised"

Question 44

what is the end point

Answer 44

this cannot be seen with the naked eye, but the point at which the indicator in the solution changes colour, this is a close approximation of equivalence

Question 45

what is a titration curve

Answer 45

equivalence can be noted a titration curve as the point at which pH changes rapidly (point of inflection).

Question 46

what are primary standards done?

Answer 46

accurately measured and mixed with distilled water to an exact volume to form a primary standard, which is accurately known concentration - the standard solution.

Question 47

what must a primary standard be ?

Answer 47

be available in pure form be stable (not react with the atmosphere) have a relatively high molar mass be soluble in a suitable solvent

Question 48

what is a primary standard

Answer 48

typically a reagent which can be weighed easily, and which is so pure that its weight is truly representative of the number of moles of substance contained

Question 49

what are the specialised glassware

Answer 49

conical flask burette pipette volumetric flask

Question 50

explain how to prepare a conical flask

Answer 50

pre-rinsed with distilled water; contains an aliquot (carefully measured volume of either the standard solution, or the 'unknown' solution)

Question 51

explain how to prepare a burette

Answer 51

pre-rinsed with reagent to be placed in it; dispenses a variable volume of either the standard solution, or the 'unknown' solution int the conical flask, where it the acid-base reaction take place

Question 52

explain how to prepare a pipette

Answer 52

pre-rinsed with reagent to be placed in it; dispenses the aliquot into hte conical flask

Question 53

explain how to prepare a volumetric flask

Answer 53

pre-rinsed with distilled water; use to prepare the standard solution to an exact known concentration.

Question 54

what is an acid

Answer 54

A chemical that gives off hydrogen ions in water and forms salts by combining with certain metals.

Question 55

what is a base

Answer 55

A base is a substance that can neutralise the acid by reacting with hydrogen ions. Most bases are minerals that react with acids to form water and salts.