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Application Exercises (Group 18)

Week 9 – Application Exercise Answers

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Question 1

(a) The burning of coal (1-6% sulfur) produces varying amounts of SO2. Once SO2 is in the air,  it reacts with oxygen molecules in the atmosphere to form SO3, which acts as a formation of aerosols.

S (s) + O2 (g) → SO2 (g) [Burning]

2 SO2 (g) + O2 (g) → 2 SO3 (g) [Reaction with Air]

Aerosols do not absorb sunlight but instead reflects it, thereby reducing visibility.

Moreover, combustion from coal plants also releases huge amounts of water vapor.

CH4 (g) + O2 (g) → CO2 (g) + 2 H2O (g)

Water vapor when cooled in the hilly forest becomes visible as fog.

(b) Natural rain is slightly acidic due to atmospheric carbon dioxide dissolving in and reacting with water to produce weak carbonic acid. Hence the approximated pH for natural rain is around pH 5.3.

Given that the pH scale is a log scale, if the acid level is 10 times stronger, it is equivalent to 1 pH more acidic. Hence, the NPCA reporting that the rain in Mammoth Cave National Park is 10 times more acidic than natural would mean that the rainfall in the park is approximately pH 4.3.

Question 2

(a) Instead of using a dryer, hang your laundry to dry it. A large portion of acid rain emissions can be attributed to power (that comes from gas or coal) generated by appliances. The idea is to use less power (reduce SO2 emission).

(b) Automobile transportation emits high levels of NOx, which contributes to the extra acidity in rain. Walk, bike, or take public transportation to work helps reduce NOx emission rate (less cars).

(c) Avoid running dishwashers and washing machines with small loads helps to reduce energy and power consumption (reduce SO2 emission).

(d) Adding additional insulation on hot water heaters and pipes helps to reduce energy use by preventing heat and cold from escaping (reduce SO2 emission).

(e) Non-locally produced food requires transportation (e.g. trucks, planes, cars, trains, boats) that are powered by fossil fuels. By purchasing locally produced and grown foods, it helps to reduce transportation-related emissions (NOx) being released to the atmosphere.

Question 3

(a) Names and chemical formulas for 5 Acids:

  1. Sulfurous acid (H2SO3)
  2. Sulfuric acid (H2SO4)
  3. Nitric acid (HNO3)
  4. Hydrochloric acid (HCl)
  5. Carbonic acid (H2CO3)

       Names and chemical formulas for 5 Bases:

  1. Sodium hydroxide (NaOH)
  2. Magnesium hydroxide (Mg(OH)2)
  3. Ammonia (NH3)
  4. Barium hydroxide (Ba(OH)2)
  5. Potassium hydroxide (KOH)

(b) 3 observable properties for Acids:

  1. Sour taste
  2. Turn blue litmus paper red
  3. pH less than 7

       3 observable properties for Bases:

  1. Bitter taste
  2. Turn red litmus paper blue
  3. pH greater than 7

Question 4

The main concern of acid rain in Singapore is the fear of wiping out native species. A study showed that 20 species of animals plentiful in the Singapore’s Bukit Timah Reserve in the 1980s, including frogs, crabs and fish are slowly being wiped out [1]. Researchers have found that the water in the stream on the nature reserves to have a pH value of 4.4 to 4.7, which is believed to be more acidic now than 20 years ago [1]. Singapore is therefore, dealing with acid rain (e.g. National Environment Agency monitoring rainfall acidity) in an aim to preserve the native species and wildlife reserves in Singapore.

Acid deposition can originate both outside and inside of the Singapore’s border. An example of acid deposition from outside is the Haze (which originates from the deforestation of Singapore’s neighboring country, Indonesia) An example of acid deposition from inside is attributed to Singapore being a tropical stream, which are naturally acidic.

[1] http://wildsingaporenews.blogspot.sg/2009/09/native-species-in-singapore-may-be.html#.WMlB3G-GOM8