About environmental science question (20 marks)

2007-10-10 5:50 am

1. The population of people in a certain island is currently 2000 an the annual population growth rate is 3%. It is estimated that the island can support 5000 people, how many years from now will the population on the island reach its carrying capacity?

2. Consider the reaction CO3^2- + H2O --> HCO3^- + OH^- , Kb = 2.1x10^-4, calculate
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the pH at which the concentration of CO3^2- and HCO3^- are equal at equilibrium.

回答 (1)

Carson

2007-10-11 7:36 am

✔ 最佳答案

1.
Let n be the years from now will the population on the island reach its carrying capacity.
2000 * 1.03^n = 5000
1.03^n = 2.5
n = log 2.5 / log 1.03
n = 30.9989
For the population on the island reach its carrying capacity it will take 31 years.
2.
CO3^2- + H2O --> HCO3^- + OH^- , Kb = 2.1x10^-4
Kb = [HCO3^-][OH^-]/[CO3^2-]
the pH at which the concentration of CO3^2- and HCO3^- are equal at equilibrium
Kb = [OH^-] = 2.1x10^-4
pKb = 3.67
pKa = 14 - 3.67 = 10.33
the pH value is 10.33

參考: My knowledge

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