acids & bases

Question 1

which metals are unreactive and how do they react with acids?

Answer 1

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.

Question 2

how do you test for sulfur dioxide gas?

Answer 2

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.

Question 3

how do you test for presence of ammonia gas?

Answer 3

Place a moist red litmus paper in the gas sample. Ammonia gas turns moist red litmus paper
blue. Ammonia gas is colourless and pungent.

Question 4

define strength of an acid

Answer 4

the strength of an acid refers to the extent to which an acid or base dissociates when dissolved in water

Question 5

define strong acid

Answer 5

A strong acid is defined as an acid that dissociates (or ionises) completely in water to form
hydrogen ions, H+

Question 6

define concentration of acids and bases

Answer 6

Concentration refers to the amount of substance (solute) dissolved in a fixed volume of solution.

Question 7

how do we classify the basicity of acids?

Answer 7

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

Question 8

ph indicator tables
- litmus
- methyl orange
- screen methyl orange
- thymol blue
- phenolphthalein

Answer 8

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

Question 9

what are the diff colors for the different pHs for universal indicator

Answer 9

pH
0 – 1 (red)
2 – 4 (orange)
5 – 6 (yellow)
7 (green)
8 – 10 (dark green)
11 – 12 (blue)
13 – 14 (violet)

Question 10

what are the metal oxides?
(define both groups)

Answer 10

1. basic oxides
   Reacts with acids
   to form salt and
   water, does not
   react with bases
2. amphoteric oxides
   - Reacts with acids
   and bases to form
   salt and water

Question 11

what are the non-metal oxides?

Answer 11

1. acidic oxides
   Reacts with bases
   to form salt and
   water, does not
   react with acids
2. neutral oxides
   Does not react with
   an acid or a base

Question 12

what are the basic oxides soluble and insoluble in water?

Answer 12

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

Question 13

what are the amphoteric oxides insoluble in water?

Answer 13

zinc oxide (ZnO)
aluminium oxide (Al2O3)
lead(II) oxide (PbO)

Question 14

what are the acidic oxides soluble and insoluble in water?

Answer 14

soluble:
nitrogen dioxide (NO2)
phosphorous(V) oxide (P2O5)
carbon dioxide (CO2)
sulfur dioxide (SO2)
sulfur trioxide (SO3)

insoluble:
silicon dioxide (SiO2)

Question 15

what are the Neutral Oxides insoluble in water?

Answer 15

carbon monoxide (CO)
nitrogen monoxide (NO)

Question 16

what is the definition of amphoteric oxides?

Answer 16

Reacts with acids
and bases to form
salt and water

Question 17

what is the definition of Basic Oxides?

Answer 17

Reacts with acids
to form salt and
water, does not
react with bases

Question 18

what is the definition of Acidic Oxides?

Answer 18

Reacts with bases
to form salt and
water, does not
react with acids

Question 19

what is the definition of Neutral Oxides?

Answer 19

Does not react with
an acid or a base

Question 20

what are the 2 grps of non metal oxides?

Answer 20

acidic oxides and neutral oxides

Question 21

what are the characteristics of carbon monoxide and how is it produced?

Answer 21

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.

Question 22

what are the characteristics of sulfur dioxide and how is it produced?

Answer 22

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.)

Question 23

what are the characteristics of oxides of nitrogen and how is it produced?

Answer 23

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.

Question 24

what are the characteristics of Unburnt hydrocarbons, methane and ozone and how are they produced?

Answer 24

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.

Question 25

what are the effects of carbon monoxide?

Answer 25

- 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

Question 26

what are the effects of sulfur dioxide and oxides of nitrogen

Answer 26

- 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

Question 27

what are the effects of unburnt hydrocarbons

Answer 27

- cause cancer (carcinogenic) - react with nitrogen oxides to form ozone

Question 28

what are the effects of methane?

Answer 28

is a greenhouse gas, which causes global warming

Question 29

what are the effects of ozone

Answer 29

- forms photochemical smog, which irritates the eyes and lungs and causes breathing difficulties - damages crops

Question 30

how is acid rain formed?

Answer 30

Acid rain is formed when acidic air pollutants such as sulfur dioxide and nitrogen dioxide react with water in the atmosphere.

Question 31

how does sulfur react with water to form acid rain?

Answer 31

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

Question 32

how does oxides of nitrogen react with water to form acid rain?

Answer 32

Oxides of nitrogen also cause acid rain. In the presence of oxygen and water, nitrogen dioxide is converted to nitric acid

Question 33

why is the pH value of unpolluted rainwater usually slightly below 7?

Answer 33

This is because carbon dioxide in the air dissolves in rainwater to form carbonic acid, which is a weak acid.

Question 34

what is the pH value of acid rain?

Answer 34

Acid rain has a pH value of 4 or less.

Question 35

what is the effect of acid rain on buildings?

Answer 35

Acid rain reacts with metals and carbonates like marble and limestone. When this happens, metal bridges and stone buildings are damaged.

Question 36

what is the effect of acid rain on plants

Answer 36

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.

Question 37

what is the effect of acid rain on aquatic life

Answer 37

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.

Question 38

what is 1 way to reduce the effects of acid rain (in denmark and sweden)

Answer 38

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.

Question 39

how is air pollution reduced using catalytic converters?

Answer 39

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: 1. Carbon monoxide is oxidised to carbon dioxide. 2CO(g) + O2(g) → 2CO2(g) 2. Oxides of nitrogen are reduced to nitrogen. 2NO(g) + 2CO(g) → N2(g) + 2CO2(g) 3. Unburnt hydrocarbons such as octane are oxidised to carbon dioxide and water. 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(g)

Question 40

what are some measures to reduce air pollution caused by motor vehicles (3 measures, state the effect for each measure as well)

Answer 40

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.

Question 41

what is flue gas desulfurisation?

Answer 41

Flue gas desulfurisation is a process of removing sulfur dioxide from the waste gases (flue gases) formed when fossil fuels undergo combustion.