Unit 6- Neutralising the Threat of Acid Rain
Question 1
Mammoth Cave National Park in Kentucky is in close proximity to the coal-fired electric utility plants in the Ohio Valley. Noting this, the National Parks Conservation Association (NPCA) reported that this national park had the poorest visibility of any in the country.
a. What is the connection between coal-fired plants and poor visibility?
Coal contains varying amounts of sulfur, hence coal-fired plants will release SO2 gas as burning of sulfur in oxygen produces SO2 gas which is poisonous.
S(s) + O2(g) -> SO2(g)
Once in the air, the SO2 can react with oxygen molecules to form sulfur trioxide.
2 SO2(g) + O2(g) -> 2 SO3(g)
SO3 then reacts with water to form sulfuric acid.
SO3(g) + H2O(l) -> H2SO4(aq)
Poor visibility, which is haze, results from tiny droplets of liquid or solid particles suspended in air. Many molecules of sulfuric acid form tiny droplets. These droplets form aerosols that do not absorb sunlight but reflect it thus reducing visibility.
b.The NPCA reported “the average rainfall in the Mammoth Cave National Park is 10 times more acidic than natural.” From this information and that in your text, estimate the pH of rainfall in the park.
pH 4
Question 2
Here are examples of what an individual might do to reduce acid rain. For each, explain the connection to producing acid rain.
a. Hang your laundry to dry it.
Requires less energy compared to using a clothes dryer, hence reduces the need for power plants to produce electricity by burning coal.
b. Walk, bike, or take public transportation to work.
Reduces gasoline used, cuts down on NOx emissions and thus reduces acidity of rain.
c. Avoid running dishwashers and washing machines with small loads.
Consume less electricity and reduces the burning of coal by power plants.
d. Add additional insulation on hot water heaters and pipes.
Reduces heat loss, thus less electricity needed to heat up the hot water, and less need for power plants to burn coal.
e. Buy locally grown produce and locally produced food
Reduces NOx emissions from vehicles (e.g. planes, ship) that bring in imported food, thus reducing acidity of rain.
Question 3
a. Give names and chemical formals for five acids and five bases.
Acids:
- Nitric acid HNO3
- Sulfuric acid H2SO4
- Hydrochloric acid HCl
- Carbonic acid H2CO3
- Hydrofluoric acid HF
Bases:
- Sodium hydroxide NaOH
- Ammonium hydroxide NH4OH
- Barium hydroxide Ba(OH)2
- Calcium hydroxide Ca(OH)2
- Lithium hydroxide LiOH
b. Name three observable properties generally associated with acids and bases.
Acids:
- Turn blue litmus paper red
- React with reactive metals to produce hydrogen gas
- Sour taste
Bases:
- Turn red litmus paper blue
- Slippery feel when dissolved in water
- Bitter taste
Question 4
The concerns of acid rain vary across the globe. Many countries in North America and Europe have websites dealing with acid rain. Either search to locate one (“Canada, acid rain”) or use these links to websites in Canada, the UK, or Europe. What are the issues in Singapore? Does the acid deposition originate outside or inside the Singapore’s borders?
URLs:
Acid rain could cause Singapore’s remaining native species to become extinct at Singapore’s Bukit Timah Nature Reserve (Straits Times ‘Native species may be wiped out by acid rain’ Sept 14 2009). However, NParks replied that the acidity of the streams may not be caused by acid rain as the streams could be naturally acidic, thus a conclusion cannot be made until more studies are done.
Acid deposition could originate inside Singapore’s borders as there are many local emitters of sulfur dioxide such as motor vehicles, refineries, power stations, shipping and other industries, according to NEA. Sulfur dioxide and NOx emission contribute to acid rain.
Source: http://wildsingaporenews.blogspot.sg/2009/09/native-species-in-singapore-may-be.html#.WMo92Pl97ic
http://www.straitstimes.com/singapore/pushing-for-higher-air-quality
