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Chem > 8.. > Flashcards

8.. Flashcards

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1
Q

Bronsted-Lowry Theory

A

defines acids and bases in terms of proton transfer between chemical compounds

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2
Q

Bronsted-Lowry acid

A

species that gives away a proton

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3
Q

Bronsted-Lowry base

A

species that accepts a proton using its lone pair of electrons

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4
Q

conjugate acid-base pairs

A

is two species that are different from each other by H+ ion

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5
Q

amphiprotic

A

species that can act both as a proton donor and acceptor

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6
Q

amphoteric

A

compounds that has both acidic and basic characters
- When the compound reacts with an acid, it shows that it has basic character
- When it reacts with a base, it shows that it’s acidic

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7
Q

reactions between metals and acids

A

acid+metals –> salt+hydrogen

  • extent of reaction depends on the reactivity of the metal and strength of acid
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8
Q

reactions between metals and oxides

A

acid + metal oxide → salt + water

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9
Q

reactions between acid and metals hydroxides

A

acid + metal hydroxide → salt + water

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10
Q

reactions between metals and carbonates

A

acid + metal carbonate → salt + water + carbon dioxide

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11
Q

reactions between metals and hydrogencarbonates

A

acid + metal hydrogencarbonate → salt + water + carbon dioxide

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12
Q

neutralization

A

A neutralisation reaction is one in which an acid (pH <7) and a base/alkali (pH >7) react together to form water (pH = 7) and a salt

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13
Q

common indicators

A

Litmus, Methyl orange, Phenolphtalein

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14
Q

color change for Litmus paper

A

color in acid - pink
color in alkali - blue

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15
Q

color change for methyl orange indicator

A

color in acid - red
color in alkali - yellow

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16
Q

color change for Phenolphtalein indicator

A

color in acid - colorless
color in alkali - pink

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17
Q

how to convert between pH and conc of H+ ions

A
18
Q

pH of acids

A

0-7
conc of H+>conc of OH

19
Q

pH of bases

A

7-14
conc of OH- > conc of H+

20
Q

Kw

A

10^-14

21
Q

universal indicator

A

acid - red
basic - violet

22
Q

strong acids

A

dissociates almost completely in aqueous solutions
- HCl (hydrochloric acid), HNO3 (nitric acid) and H2SO4 (sulfuric acid)
- irreversible reactions

23
Q

weak acids

A

weak acid is an acid that partially (or incompletely) dissociates in aqueous solutions
- organic acids (ethanoic acid), HCN (hydrocyanic acid), H2S (hydrogen sulfide) and H2CO3 (carbonic acid)
- equilibrium

24
Q

Strong bases

A

base that dissociates almost completely in aqueous solutions
- group 1 metal hydroxides such as NaOH (sodium hydroxide)
- irreversible reactions

25
Q

weak bases

A

base that partially (or incompletely) dissociates in aqueous solutions
- NH3 (ammonia), amines and some hydroxides of transition metals
- equilibrium

26
Q

strong acids produce _________ conjugate bases

A

weak

27
Q

weak acids produce _______ conjugate bases

A

strong

28
Q

how can strong and weak acids be distinguished

A
  • pH values
  • electrical conductivity
  • reactivity
29
Q

electrical conductivity of strong acids vs weak acids

A
  • ## strong acids have a higher concentration of H+, so they conduct electricity better
30
Q

reactivity of strong acids vs weak acids

A
  • strong and weak acids of the same concentrations react differently with reactive metals
  • this is bc the concentration of H+ is greater in strong acids compared to weak acids
  • ## The greater H+ concentration means that more H2 gas is produced in a shorter time
31
Q

acid deposition

A
  • Rain is naturally acidic because of dissolved CO2 which forms carbonic acid
    H2O (l) + CO2 (g) ⇌ H2CO3 (aq)
  • Carbonic acid is a weak acid and dissociates in the following equilibrium reaction giving a pH of 5.6
    H2CO3 (aq) ⇌ H+ (aq) + HCO3- (aq)

For that reason acid rain is defined as rain with a pH of below 5.6
Acid deposition includes all processes by which acidic components leave the atmosphere
- This could be gases or precipitates

There are two types of deposition: wet acid deposition and dry acid deposition
- Wet acid deposition refers to rain, snow, sleet, hail, fog, mist and dew
- Dry acid deposition refers to acidic particles and gases that fall to the ground as dust and smoke
- Acid deposition is formed when nitrogen or sulfur oxides dissolve in water to form HNO3, HNO2, H2SO4 and H2SO3

32
Q

Formation of sulfur based acids

A
  • fossil fuels are often contaminated with small amounts of sulfur impurities
  • when these contaminated fossil fuels are combusted, the sulfur in the fuels get oxidised to sulfur dioxide
  • sulfur dioxide may be further oxidised to sulfur trioxide
  • the sulfur dioxide and trioxide then dissolve in rainwater droplets to form sulfurous acid (H2CO3) and sulfuric acid (H2CO3)
  • these acids are components of acid rain which has several damaging impacts on the environment
33
Q

formation of acid rain by nitrogen oxides

A
  • the temperature in an internal combustion engine can reach 2000 °C
  • nitrogen and oxygen, which at normal temperatures don’t react, comine to form nitrogen monoxide
  • nitrogen monoxide reacts further forming nitrogen dioxide
  • nitrogen dioxide gas rects with rain water to form a mixture if nitrous and nitric acids, which contribute to acid rain
  • lightning can also trigger the formation of nitrogen monoxide and nitrogen dioxide in the air
  • -
34
Q

effects of acid deposition on materials

A
  • acid deposition can react with metals and rocks (limestone) causing buildings and statues to get damaged
  • limestone and marble both contain CaCO3
  • calcium carbonate reacts with sulfuric or nitric acids causing stoneworks to corrode or weaken
  • metallic structures, such as iron bridges, are vulnurable to corrosion by wet and dry deposition forming the salt of the metal
35
Q

what is the effects of acid deposition on plants

A
  • Apart from acid deposition directly falling on leaves and killing plants, acid particulates can block stomata ( plant pores) and prevent gaseous exchange
  • Acid rain can fall on soils and release important minerals such as magnesium, calcium and potassium which are leached (washed out) from soils and are therefore unavailable to plants
  • Aluminium ions released from rocks are toxic to many plants and damage their roots
36
Q

acid deposition effects on water

A
  • When acid rain falls on rivers and lakes the pH can fall to levels that are unable to support life
  • Below about pH 4, aluminium ions are released from rocks when they are held as aluminium hydroxide
  • Alumnium ions are toxic to fish as they damage the gills and prevent fish from efficiently absorbing oxygen
  • Nitrate ions from nitric acid in acid rain can contibute to over-fertilization of waterways and lead to eutrophication
  • Eutrophication is excessive algal growth that results in oxygen depletion and stagnation of waterways
37
Q

acid deposition effects on human health

A
  • no direct impact on skin
  • however, acid particulates in the air can increase the risk of respiratory diseases
  • When acid rain comes into contact with metal pipes there is an increased risk that toxic metal ions will be released into the water supply such as Cu2+, Al3+ and Pb2
38
Q

2 ways to reduce sulfur oxide emissions

A
  • removal of sulfur from fossil fuels can either take place pre-combustion or post-combustion
  • SO2 and SO3 are both acidic and toxic
  • sulfur dioxide is produces naturally during volcanic eruptions
  • large quantities have been emitted by burning coal, oil and natural gas
39
Q

reducing sulfur oxides via pre-combustion

A
  • Pre-combustion takes place for coal and petroleum, altough it is expensive to remove all the sulfur, so a small percentage often remains
  • essential to remove most of the sulfur as it damamges the workings of the internal combustion engines
  • sulfur is removed by reacting it with hydrogen - hydrodesulfurization
  • sulfur is recovered and used in the manifacture of sulfuric acid
40
Q

reducing sulfur oxides via post-combustion

A
  • carried out in a coal fired power stations
  • the waste gases from burning the coal contain sulfur dioxide
  • the waste gases are passed through a wet slurry of calcium oxide and calcium carbonate which react with SO2 and produce calcium sulfate
  • calcium sulfate is also known as gypsum and is used to make plsterboard and other useful building materials

Chem (13 decks)

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