acids & bases Flashcards
which metals are unreactive and how do they react with acids?
However, not all metals will react with acids to give a salt and hydrogen gas.
When unreactive metals such as copper, silver or gold are added to dilute acids, there is no
reaction.
Lead appears not to react with dilute hydrochloric acid and dilute sulfuric acid. The initial reaction between lead and dilute acid produces a layer of lead(II) chloride or lead(II) sulfate which are insoluble in water and quickly forms a coating around the metal. The coating prevents the metal
from further reaction with the acid.
how do you test for sulfur dioxide gas?
Place a strip of filter paper soaked in acidified potassium manganate(VII) solution in the gas sample. Sulfur dioxide gas turns purple acidified potassium manganate(VII) colourless.
Sulfur dioxide also turns orange acidified potassium dichromate(VI) green.
how do you test for presence of ammonia gas?
Place a moist red litmus paper in the gas sample. Ammonia gas turns moist red litmus paper
blue. Ammonia gas is colourless and pungent.
define strength of an acid
the strength of an acid refers to the extent to which an acid or base dissociates when dissolved in water
define strong acid
A strong acid is defined as an acid that dissociates (or ionises) completely in water to form
hydrogen ions, H+
define concentration of acids and bases
Concentration refers to the amount of substance (solute) dissolved in a fixed volume of solution.
how do we classify the basicity of acids?
acids are classified as monobasic, dibasic, tribasic depending on the number of H atoms in a molecule that are able to form H+ ions when it dissociates in water
ph indicator tables
- litmus
- methyl orange
- screen methyl orange
- thymol blue
- phenolphthalein
litmus: red blue 5 – 8
methyl orange: red yellow 3 – 5
screened methyl orange: pink green 3 – 5
thymol blue: yellow blue 8 – 10
phenolphthalein: colourless pink 8 – 10
what are the diff colors for the different pHs for universal indicator
pH
0 – 1 (red)
2 – 4 (orange)
5 – 6 (yellow)
7 (green)
8 – 10 (dark green)
11 – 12 (blue)
13 – 14 (violet)
what are the metal oxides?
(define both groups)
- basic oxides
Reacts with acids
to form salt and
water, does not
react with bases - amphoteric oxides
- Reacts with acids
and bases to form
salt and water
what are the non-metal oxides?
- acidic oxides
Reacts with bases
to form salt and
water, does not
react with acids - neutral oxides
Does not react with
an acid or a base
what are the basic oxides soluble and insoluble in water?
soluble in water:
potassium oxide (K2O)
sodium oxide (Na2O)
lithium oxide (Li2O)
calcium oxide (CaO)
barium oxide (BaO)
insoluble in water:
magnesium oxide (MgO)
copper(II) oxide (CuO)
iron(II) oxide (FeO)
iron(III) oxide (Fe2O3
what are the amphoteric oxides insoluble in water?
zinc oxide (ZnO)
aluminium oxide (Al2O3)
lead(II) oxide (PbO)
what are the acidic oxides soluble and insoluble in water?
soluble:
nitrogen dioxide (NO2)
phosphorous(V) oxide (P2O5)
carbon dioxide (CO2)
sulfur dioxide (SO2)
sulfur trioxide (SO3)
insoluble:
silicon dioxide (SiO2)
what are the Neutral Oxides insoluble in water?
carbon monoxide (CO)
nitrogen monoxide (NO)
what is the definition of amphoteric oxides?
Reacts with acids
and bases to form
salt and water
what is the definition of Basic Oxides?
Reacts with acids
to form salt and
water, does not
react with bases
what is the definition of Acidic Oxides?
Reacts with bases
to form salt and
water, does not
react with acids
what is the definition of Neutral Oxides?
Does not react with
an acid or a base
what are the 2 grps of non metal oxides?
acidic oxides and neutral oxides
what are the characteristics of carbon monoxide and how is it produced?
Carbon monoxide is a colourless and odourless gas. Much of the carbon monoxide in the air
comes from the incomplete combustion of petrol in car engines.
what are the characteristics of sulfur dioxide and how is it produced?
Fossil fuels such as coal, crude oil (petroleum) and natural gas contain sulfur. When they are
burnt in motor vehicles, power stations and factories, sulfur is converted to sulfur dioxide.
(Sulfur dioxide is also produced in large quantities during volcanoes eruptions.)
what are the characteristics of oxides of nitrogen and how is it produced?
In a car engine or chemical factory, where temperatures are very high, nitrogen combines
with oxygen in the air to form nitrogen monoxide or nitric oxide (NO).
Nitrogen monoxide reacts with oxygen to form a brown gas, nitrogen dioxide (NO2).
During thunderstorms, heat energy released by lightning causes nitrogen and oxygen in the
air to react to form oxides like nitrogen monoxide and nitrogen dioxide.
what are the characteristics of Unburnt hydrocarbons, methane and ozone and how are they produced?
Unburnt hydrocarbons are released in car exhaust fumes and chemical plants.
Methane is a colourless and odourless gas, which is produced when plant and animal matter
decay. Sheep and cows give off methane due to digestion of food. Methane is also produced
from the decay of rubbish in landfills.
Ozone is formed when nitrogen dioxide in the air reacts with unburnt hydrocarbons in the
presence of sunlight.
what are the effects of carbon monoxide?
- reacts with haemoglobin in blood to form
carboxyhaemoglobin, which reduces the ability of
haemoglobin to transport oxygen to the rest of the body - causes headaches, fatigue, breathing difficulties and even death
what are the effects of sulfur dioxide and oxides of nitrogen
- irritate the eyes and lungs and cause breathing difficulties
- high levels lead to inflammation of the lungs (bronchitis)
- react with water in the atmosphere to form acid rain,
which corrodes buildings and harms aquatic life and plants
what are the effects of unburnt hydrocarbons
- cause cancer (carcinogenic)
- react with nitrogen oxides to form ozone
what are the effects of methane?
is a greenhouse gas, which causes global warming
what are the effects of ozone
- forms photochemical smog, which irritates the eyes and lungs and causes breathing difficulties
- damages crops
how is acid rain formed?
Acid rain is formed when acidic air pollutants such as sulfur dioxide and nitrogen dioxide
react with water in the atmosphere.
how does sulfur react with water to form acid rain?
Sulfur dioxide dissolves in water to form sulfurous acid. In the presence of oxygen in the air, sulfurous acid is slowly oxidised to sulfuric acid
how does oxides of nitrogen react with water to form acid rain?
Oxides of nitrogen also cause acid rain. In the presence of oxygen and water, nitrogen
dioxide is converted to nitric acid
why is the pH value of unpolluted rainwater usually slightly below 7?
This is because carbon
dioxide in the air dissolves in rainwater to form carbonic acid, which is a weak acid.
what is the pH value of acid rain?
Acid rain has a pH value of 4 or less.
what is the effect of acid rain on buildings?
Acid rain reacts with metals and carbonates like marble and limestone. When this happens, metal bridges and stone buildings are damaged.
what is the effect of acid rain on plants
Acid rain leaches nutrients from soil and causes plants to wither and die. Acid rain may also react with aluminum hydroxide (Al2O3) in the soil to produce Al3+ ions which are toxic to plants.
what is the effect of acid rain on aquatic life
Acid rain reduces the pH value of natural water bodies like lakes and streams, from between 6.5 and 8.5 to below 4, which is too acidic for fish and other aquatic life to survive.
what is 1 way to reduce the effects of acid rain (in denmark and sweden)
powdered limestone (calcium carbonate) is used to neutralise and hence restore lakes and rivers polluted by acid rain. This is called liming. However, this method is expensive and its effect are only temporary.
how is air pollution reduced using catalytic converters?
To reduce air pollution, the exhaust systems of most cars are fitted with catalytic converters. The harmful pollutants are converted into harmless substances by redox reactions:
- Carbon monoxide is oxidised to carbon dioxide.
2CO(g) + O2(g) → 2CO2(g) - Oxides of nitrogen are reduced to nitrogen.
2NO(g) + 2CO(g) → N2(g) + 2CO2(g) - Unburnt hydrocarbons such as octane are oxidised to carbon dioxide and water.
2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(g)
what are some measures to reduce air pollution caused by motor vehicles (3 measures, state the effect for each measure as well)
measure: Use new materials such as lightweight
alloys, instead of steel, to make car
bodies
effect: Less fuel is needed to power lighter car
bodies.
measure: Use clean fuels, such as methanol and
hydrogen
effect: The products of combustion are harmless.
E.g. When hydrogen burns, only water is
produced.
measure: Use electric cars
effect: Battery-powered cars reduce exhaust gas
emissions.
what is flue gas desulfurisation?
Flue gas desulfurisation is a process of removing sulfur dioxide from the waste gases (flue
gases) formed when fossil fuels undergo combustion.
