20. How many chemical reactions are possible regarding the formation of carbonic acid and the dissolving of calcite?
A. 23 B. 3 C. 2 D. 10
Ocean acidification is the name given to the ongoing decrease in the pH of the Earth's oceans, [ caused by the uptake of anthropogenic carbon dioxide (CO2) from the atmosphere. About 30–40% of the carbon dioxide released by humans into the atmosphere dissolves into the oceans, rivers and lakes. To maintain chemical equilibrium, some of it reacts with the water to form carbonic acid.
Some of these extra carbonic acid molecules react with a water molecule to give a bicarbonate ion and a hydronium ion, thus increasing the ocean's "acidity" (H+ ion concentration). Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.25 to 8.14, representing an increase of almost 30% in H+ ion concentration in the world's oceans.
This increasing acidity is thought to have a range of direct undesirable consequences such as depressing metabolic rates in jumbo squid, depressing the immune responses of blue mussels. and coral bleaching.
Other chemical reactions are also triggered which result in an actual net decrease in the amount of carbonate ions available. In the oceans, this makes it more difficult for marine calcifying organisms, such as coral and some plankton, to form biogenic calcium carbonate, and existing such structures become vulnerable to dissolution. Thus, ongoing acidification of the oceans also poses a threat to the food chains connected with the oceans. As members of the InterAcademy Panel, 105 science academies have issued a statement on ocean acidification. The statement recommends that by 2050, global CO2 emissions be reduced by at least 50%, compared to the 1990 level. ]
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