module six - revision deck

Question 1

hydrochloric acid

Answer 1

HCl - strong

Question 2

Hydrofluoric Acid

Answer 2

HF - weak

Question 3

Sulfuric Acid

Answer 3

H2SO4 - strong

Question 4

Nitrous Acid

Answer 4

HNO2 - weak

Question 5

Nitric Acid

Answer 5

HNO3 - strong

Question 6

phosphoric acid

Answer 6

H3PO4 - weak

Question 7

carbonic acid

Answer 7

H2CO3 - weak

Question 8

Sodium Hydroxide

Answer 8

NaOH - strong

Question 9

Calcium Hydroxide

Answer 9

Ca(OH)2 - strong

Question 10

Barium Hydroxide

Answer 10

Ba(OH)2 - strong

Question 11

Sodium Carbonate

Answer 11

Na2CO3 - weak

Question 12

Sodium Bicarbonate

Answer 12

NaHCO3 - weak

Question 13

ammonia

Answer 13

NH3 - weak

Question 14

litmus

Answer 14

red below pH 5

blue above pH 7.6

Question 15

Methyl Orange

Answer 15

Red below pH 3.1

Yellow above pH 4.4

Question 16

bromothymol blue

Answer 16

yellow below pH 6

blue above pH 7.6

Question 17

phenolphthalein

Answer 17

colourless below pH 8.3

pink above pH 10.0

Question 18

acid/base reaction

Answer 18

acid + base –> salt + water

Question 19

acid/carbonate reaction

Answer 19

acid + carbonate –> salt + water + carbon dioxide

Question 20

acid/metal reaction

Answer 20

dilute acid + active metal –> salt + hydrogen gas

Question 21

applications of neutralisation - household

Answer 21

antacids - contain bases e.g. mg(OH)2 to neutralise excess HCl in the stomach

toothpaste - alkaline to neutralise the acid in the mouth and to remove food particles that produce acid when they decay

formic acid from bee or ant stings is neutralised by using creams containing bases

Question 22

applications of neutralisation - industry

Answer 22

slaked lime (calcium hydroxide) or limestone (calcium carbonate) is added to neutralise acid in soil for agriculture

gypsum (calcium sulfate) can be used to neutralise alkaline soil

wastewater from industrial processes is acidic or alkaline so needs to be neutralised before entering waterways

Question 23

lavoisier model of acids

Answer 23

1780 - Antoine Lavoiser
defined acids as substances containing oxygen
e.g. H2SO4
not all acids contain oxygen (HCl)

Question 24

Davy model of acids and bases

Answer 24

Humphry Davy (1815) 
concluded that acids contain hydrogen
didn't explain why some compounds that contain hydrogen don't behave like an acid

Question 25

Arrhenius model

Answer 25

``` Svante Arrhenius (1884) suggested acids were substances that produced hydrogen ions in aqueous solutions, and that bases produced OH ions in aqueous solutions ``` doesn't explain why substances that don't contain hydroxide act like bases (NH3) limited to reactions in aqueous solution, so doesn't explain acid-base reactions in other states

Question 26

Bronsted-Lowry Model

Answer 26

1923 proposed that an acid-base reaction involved protons being transferred between reaction components and states that acids are proton donors and bases are proton acceptors does not explain the acidity of acid oxides (SO2 and SO3) and their reactions with basic oxides (CaO)

Question 27

concentration definition

Answer 27

the amount of solute in a specified amount of solution

Question 28

strength

Answer 28

the degree to which an acid ionises or a base dissociates - strong acids are acids in which almost all of the acid molecules ionise to produce a hydrogen ion

Question 29

conjugate acid/base pairs

Answer 29

members of a conjugate acid-base pair differ from each other by the presence or absence of the transferrable H the conjugate base of an acid has one less proton the conjugate acid of a base has one more proton

Question 30

amphiprotic

Answer 30

a substance that can donate or accept a proton | e.g. HSO4, H2O, H2PO4

Question 31

equivalence point

Answer 31

the point in a titration where the amount of titrant added is enough to completely neutralise the analyte solution

Question 32

end point

Answer 32

the physical sign that the equivalence point has been reached i.e. when the indicator changes colour

Question 33

titrant

Answer 33

substance you want to determine the concentration of

Question 34

aliquot

Answer 34

volume measured by the pipette

Question 35

titre

Answer 35

volume delivered by the burette

Question 36

primary standard

Answer 36

a chemical that can be made up into a solution of accurately known concentration

Question 37

properties of primary standards

Answer 37

- available in highly pure form - large molar mass - stable in air - does not absorb moisture or CO2 from the air - readily soluble in distilled water - reacts readily with solution of known concentration

Question 38

when back titrations are needed

Answer 38

- it is difficult to determine a definite end point because the reaction occurs too slowly - the sample is not soluble in water, but will react with another acid - the sample is toxic - the sample is volatile - the sample is gaseous and in a mixture of gases - the sample is fairly unreactive

Question 39

Ka

Answer 39

for HA + H2O(l) H3O+ + A- Ka = [H3O+][A-]/[HA-]

Question 40

Ka of weak vs strong acids

Answer 40

Ka of weak acids is very small | Ka of strong acids is very large

Question 41

percentage ionisation

Answer 41

percentage of an acid that has been ionised in water [A-]/[HA] x 100

Question 42

pKa

Answer 42

pKa = -log10 Ka smaller pKa corresponds to greater acid strength

Question 43

Kb

Answer 43

for B + H2O(l) BH+ + OH- Kb = [BH+][OH-]/[B]

Question 44

relationship between Ka and Kb

Answer 44

Ka x Kb = Kw = 1.01x10^-14

Question 45

acid base techniques - winemaking

Answer 45

wine mainly contains tartaric acid, malic acid and citric acid and has a pH of about 2.5 to 4 back titrations are often used to find the alcohol content in wine

Question 46

acid base techniques - mining

Answer 46

need to know the composition of ores, metals and alloys | sample are dissolved in acid then titrated to find the composition

Question 47

acid base techniques - water treatment

Answer 47

both acids and bases are used to treat drinking water and waste water to ensure they have a pH of around 7 HCl is commonly used to lower the pH Mg(OH)2 or NaOH used to raise the pH neutralisation process prevents highly acidic or basic water flowing through pipes and corroding them

Question 48

Acid Base techniques by ATSI people

Answer 48

Soap Tree (Alphitonia Excelsa) - used by the Kuku Yalanji people of the Daintree - leaves contain saponins which tend to be acidic - the wood, bark and leaves contain many organic acids and small amounts of methyl salicylate - methyl salicylate is thought to be responsible for the analgesic properties of the plant - one end of the saponin molecule is hydrophilic while the other is hydrophobic, which explains its ability to act as a mild soap - used on the skin as a cleanser and as an antiseptic for treating rashes and ringworm

Question 49

buffers

Answer 49

maintain a pH within a certain range despite the addition of an acid or base occurs in a conjugate acid base pair where the acid is weak

Question 50

ability of buffers

Answer 50

the ability of buffers to resist changes in pH depends on the conjugate acid/base - higher initial concentration of conjugate acid and base means a greater capacity for a buffer to resist changes to its pH - a buffer should have equal ability to resist changes from acids and bases

Question 51

blood buffers

Answer 51

blood needs to be in a pH range of 7.35 to 7.45 CO2 + H2O H2CO3 H2CO3 + H2O HCO3 - + H3O+ carbon dioxide converts into acid when dissolved in blood

Question 52

ocean buffer

Answer 52

ocean absorbs CO2 from atmosphere CO2 + H2O H2CO3 H2CO3 + H2O HCO3 - + H3O+ ocean buffer systems are unable to combat the increase in CO2, increasing the oceans acidity

Question 53

cells buffers

Answer 53

cells need pH close to neutral intracellular fluid contains phosphate buffer system H2PO4 + H2O HPO42- + H3O+