Sulphuric Acid

Question 1

what was the acid originally called

Answer 1

oil of vitriol (initially prepared by distilling green vitriol)

Question 2

occurence in free state

Answer 2

hot springs, near sulphide beds

Question 3

general methods of prep

Answer 3

1. action of heat on nitric acid and sulphur
2. passage of chlorine through aqueous solution of sulphur dioxide
3. dissolution of sulphur dioxide in water
4. hydrolysis of sulphuryl chloride

Question 4

production of SO2 in contact process

Answer 4

1. blower: for passage of pure air or oxygen
2. sulphur or pyrite burners: producing SO2 by burning sulphur or iron pyrites

Question 5

purification units of contact process

Answer 5

1. dusting tower
2. cooling pipes:
3. scrubbing tower:
4. drying tower:
5. arsenic purifier
6. testing box

Question 6

dusting tower

Answer 6

removal of dust by downward blow of steam

Question 7

cooling pipes

Answer 7

for cooling the gases by passage through isolated pipes

Question 8

scrubbing tower

Answer 8

further removal of impurities by downward spray of water

Question 9

drying tower

Answer 9

dry moist gases by spray of concentrated sulphuric acid

Question 10

arsenic purifier

Answer 10

removing arsenic oxide by passage over ferric hydroxide

Question 11

testing box

Answer 11

testing purity of gases by passing light through darkened box

Question 12

processes of contact process

Answer 12

1. production of SO2
2. purification unit
3. catalytic oxidation
4. absorption of SO3
5. dilution of Oleum

Question 13

conditions of catalytic oxidation of sulphur dioxide

Answer 13

catalyst: vanadium pentoxide OR platinum
temp: 450-500 degrees
pressure: 1-2 atmos
conversion ration: 98% of sulphur dioxide is converted to trioxide
exothermic!
decrease in volume

Question 14

what happens in absorption tower of contact process

Answer 14

absorption of SO3 in 98% sulphuric acid to give oleum/ pyrosulphuric acid (H2S2O7)

Question 15

why is burning of sulphur or iron pyrites in oxygen preferred to pure air

Answer 15

heat energy is wasted in heating the unreactive nitrogen component of the air

Question 16

why should impurities be removed in contact process

Answer 16

impurities poison the catalyst

Question 17

why is vanadium pentoxide preferred over platinized asbestos as catalyst

Answer 17

cheap and less easily poisoned

Question 18

promoter used in contact process

Answer 18

potassium oxide

Question 19

why is sulphur trioxide first absorbed into sulphuric acid, and not into water directly?

Answer 19

the reaction of water and SO3 is highly exothermic, forming a dense fog of sulphuric acid particles which do not condense easily

Question 20

nature of sulphuric acid

Answer 20

dense, oily, hygroscopic liquid (absorbs moisture)

Question 21

density of acid

Answer 21

1.85 (heavier than water)

Question 22

solubility of acid

Answer 22

soluble in water in all proportions

Question 23

at what temp does acid form a constant boiling mixture

Answer 23

at 338 degrees, containing 98% of acid

Question 24

BP of sulphuric acid

Answer 24

338 C

Question 25

melting/freezing point of sulphuric acid

Answer 25

10.4 C

Question 26

conductivity of sulphuric acid

Answer 26

pure acid: non conductor
dilute: good conductor

Question 27

why is acid added to water, and water not added to acid (for dilution)?

Answer 27

when water is added to acid, there is a sudden increase in temperature and acid spurts out
when acid is added to water, the acid being heavier settles down and evolved heat in dissipated in the water itself and spurting is minimized.

Question 28

define constant boiling mixture

Answer 28

one which boils without change in composition

Question 29

why does dilute sulphuric acid act acidic

Answer 29

due to presence of hydronium ions formed when H2SO4 dissociates in aq. soln.

Question 30

chemical properties of sulphuric acid

Answer 30

1. acidic nature when dilute
2. dibasic (dissociates into two hydrogen ions)
3. non volatile acid
4. oxidising agent
5. dehydrating agent (strong affinity to water)

Question 31

why does hydrogen form two types of salts with an alkali

Answer 31

it forms one acid salt and one basic salt since its basicity is two.

Question 32

why is conc. sulphuric acid a good oxidising agent

Answer 32

H2SO4 on thermal decomposition gives nascent oxygen, which helps in oxidation

Question 33

what are some gases that are not dried by conc. H2SO4

Answer 33

H2S and NH3 react with conc. sulphuric acid, hence the acid is not used as a drying agent with them.

Question 34

formula of formic acid

Answer 34

H.COOH

Question 35

formula of oxalic acid

Answer 35

H2C2O4

Question 36

formula for ethanol/ ethyl alcohol

Answer 36

C2H5OH

Question 37

formula of ethene

Answer 37

C2H4

Question 38

what does dehydration of ethanol give

Answer 38

ethene and water

Question 39

observation when conc. sulphuric acid is added to cane sugar

Answer 39

1. black spongy mass of carbon formed
2. steam is evolved

Question 40

test for concentrated sulphuric acid

Answer 40

action of heat on copper or sodium chloride, with conc. acid

Question 41

test for dilute sulphuric acid

Answer 41

addition of barium chloride solution/ lead nitrate soln. to dilute acid
(insoluble white precipitates for both are formed.

Question 42

how to distinguish sulphuric acid and hydrochloric acid using lead nitrate soln

Answer 42

H2SO4: lead sulphate formed is insoluble in hot water or even on heating
HCl: lead chloride formed is soluble in hot water

Question 43

how to distinguish sulphuric acid, hydrochloric acid, and nitric acid (dilute), using barium chloride

Answer 43

H2SO4: white ppt of barium sulphate formed
HCl: no white ppt formed
HNO3: no white ppt formed