Question

Read the following scenario and answer the questions below.
Acid drainage is one of the most prevalent environmental impacts of mining. Mining exposes rock walls to air, sulphide minerals in the rock react with water and oxygen from air, forming sulphuric acid. Metals began to leach from the rock walls into the acidic water, including iron, zinc, aluminum, manganese, nickel, cadmium, cobalt, arsenic, and copper. The metals react with sulphuric acid to form metal sulphates. High concentrations of these dissolved metals make the water toxic to wildlife, and waterfowl landing at the site is often found dead. To alleviate this problem, a group of scientists proposed a cleanup using a bioreactor, in which sulphate-reducing bacteria take sulphate ions ( SO42-) from the mine water and use carbon-based organic compounds (CH2O) to create hydrogen sulphide (H2S), which smells like rotten eggs, and bicarbonate (HCO3- ): SO42-+ 2CH2O → H2S + 2HCO3-. The produced hydrogen sulphide is removed from the bioreactor and fed back to the metal precipitation tanks, where it drives reactions in which metal ions bond to sulphur atoms to form dark-coloured metal sulphides, which are insoluble in water and thus precipitate into a solid, settling to the bottom. For example, with the metal zinc (Zn), the equation would be as follows: H2S+Zn2+ → ZnS + 2H+. The metal sulphides are then removed from the precipitation tanks. Precipitates of the various metals ranged in purity from 75% to 98%. The acidity associated with hydrogen ions H+ is buffered with the help of bicarbonate produced by the bacteria.
Which of the following is NOT true?
A) Sulphate-reducing bacteria are chemoautotrophic.
B) The method mimics some natural processes.
C) Metal sulphates are more soluble in water than metal sulphides.
D) Bicarbonate can be used to prevent a lowering of pH.
E) Zinc in solids is less dangerous to wildlife than zinc in its dissolved form.

Answer

This answer is hidden. It contains 1 characters.