Acidic Environment 2

Question 1

Oxides of non metals

Answer 1

are acidic oxides that react with water to form acidic solutions.
Acidic oxide + water –> acid
e.g. CO2 + H2O –> H2CO3 (carbonic acid)
Acidic oxides can react with bases to form salts
acidic oxide + base —> salt + water
E.g. CO2 + 2 NaOH –> H20 +Na2CO3

Question 2

Oxides of metals

Answer 2

generally basic oxides.
Soluble metal oxides produce alkaline solutions.
e.g MgO + H20 –> Mg(OH)2
Basic oxides react with acids to form salts.
e.g MgO + 2HCl –> MgCl2 + H2O
DO NOT REACT WITH ALKALI SOLUTIONS

Question 3

amphoteric oxides

Answer 3

react with acids and alkalis

e.g. zn, Pb, Sn, As, Al)

Question 4

Neutral oxides

Answer 4

CO, NO and N2O do not react with either acids OR bases.

Question 5

relationship between position of non metals in periodic table and acidity/basicity of oxides.

Answer 5

metals give way to non-metals (–> table)
Basic oxides (ionically bonded together) –> few amphoteric oxides –> acidic oxides (covalently bonded)
Noble (inert) gases do not form oxides.
Some acidic oxides in groups IV to VII show a trend from weakly acidic to strongly acidic in going across these groups.

Question 6

define le chateliers principle

Answer 6

The concentrations of reactants and products in a mixture @ equilibrium will alter so as to counteract any change in concentration, temp or gas pressure

Question 7

changing temperature of equilibrium

Answer 7

shifts to minimise the effect of the change. if reaction is endothermic, reaction will –>
If exothermic, reaction will shift to

Question 8

Changing he pressure of

Answer 8

ONLY IF IT INVOLVES GASES

if pressure is increased, will favour the side with the lower amount of substances.

Question 9

4 features of a system at

Answer 9

• closed system
• reactant/product concentrations remain constant
• continual microscopic changes
• Rate of forward reaction = rate of reverse reaction

Question 10

Solubility of Carbon dioxide in water under various conditions as an equilibrium process

Answer 10

• From air, CO2 dissolves sparingly in water
  CO2(g) CO2 (aq)
  the dissolved CO2 reacts with H2O to form a weak solution of carbonic acid that slightly dissociates:
  CO2(aq) + H2O (l) H+ (aq) + HCO3-(aq)
• If pressure on CO2 increases, more gas goes into solution in attempt to counteract this increase.
• Dissolving process is exothermic. (if temp increases, moves to left to absorb heat and counteract change)
• If solution is made alkaline, the H+ (aq) reacts with the OH- ion, destabilising the and so the solubility of CO2 increases.

Question 11

Natural and industrial sources of Sulfur Dioxide

Answer 11

Sulfur dioxide is an acidic oxide found in the atmosphere.
NATURAL:
* emissions from volcanoes/hot springs
*oxidation of hydrogen sulfide produced during the decay of organic matter
INDUSTRIAL:
* smelting sulfide ores during conversion of minerals into metals.
* Combustion of fossil fuels (coal and oil)
* burning organic matter (bushfires)

Question 12

Natural and industrial sources of oxides of nitrogen

Answer 12

N20, NO, NO2 (NOx)
NATURAL: 
* Lightning strikes can join N and O together. Eventually leads to nitrates that fertilise soils.
* formed by soil bacteria
INDUSTRIAL:
* at high temps (inside engines or power stations), N and O in atmosphere can combine to form NOx
* Burning fossil fuels and vegetation 
* formed by vehicle catalytic converters

Question 13

Reactions with SO2

Answer 13

• In the combustion of fossil fuels, sulfur contained in sulfur compounds and oxygen react to produce sulfur dioxide.
  S(s) + O2 (g) –> SO2 (g)
• In a metal Sulfide smelter, metal sulfide and oxygen react to produce a metal oxide and sulfur dioxide.
  2ZnS (s) + 3O2 (g) –> 2ZnO (s) + 2SO2(g)

Question 14

Reactions with nitrogen oxides

Answer 14

• High temps produced by lightening strikes and combustion allow N and O in atmosphere to react to produce nitric oxide.
  N2 (g) + O2 (g) –> 2NO(g)
• Nitric oxide and O in atmosphere react slowly to produce nitrogen dioxide.
  2NO (g) + O2 (g) –> 2NO2(g)

Question 15

+ of sulfur and nitrogen.

Answer 15

• Vehicles and industries are largely responsible for these gases in the atmosphere.
• As No2 and SO2 are regularly flushed out of the atmosphere by rain, there appears not to have been any appreciable build up during the 20th century.
• lack of reliable data as only recently has technology been able to measure Concentrations of these gases below 0.1ppm.
• N20 increased by 15% and CO2 increased by 30% over last 150 years.

Question 16

Formation of acid rain

Answer 16

Rain water is slightly acidic because it contains dissolved acidic oxides (CO2, SO2, NO2) that form weak acids
e.g. Nitrogen dioxide reacts w water to form nitrous and nitric acids:
2NO2(g) + H2O (l) –> HNO2 (aq) + HNO3(aq)

Question 17

Effects of acid rain

Answer 17

• acidity in soil is affected which stunts plant growth and causes defoliation.
• Sulfates and Hydrogen sulfates from sulphuric acids can leach out essential plant chemicals (Ca, Mg) from soil.
• Some animas sensitive to changes in acidity levels (especially aquatic organisms) and can affect their reproduction or kill them.
• Corrosion and decay of buildings (esp. those made of Calcium carbonate such as limestone and marble).

Question 18

how can we prevent acid rain

Answer 18

prevent SO2 and NO2 from industries and vehicles escaping into the atmosphere.
In many countries there are now legal limits of quantity of these pollutants that factories can emit. However we cannot control natural sources of these chemicals.