Question

1. Imagine you have two beakers: one with 750 ml of sea water and one with 750 ml of distilled water. You bubble CO2 into each and take the pH of each solution every minute for 15 minutes.

Q1: Why did pH decrease when CO₂ was added to water and sea water?

Q2: Why did the pH of the water decrease more quickly than the sea water?

1. Explain how the buffer system in our blood is related to ocean acidification.

According to the video “Changing Waters on the Oregon Coast”:

1: What aquatic organisms are most vulnerable to ocean acidification?

Q2: Why will the Oregon coast continue to see an increase in ocean acidification for 30-35 years even if we were to completely stop CO2 emissions today and cap the atmospheric levels?

Answer 1

1) The pH decrease when CO2 was added in the water. It is because when CO2 is converted into H2O .It results in the conversion of H+ ( Hydrogen positive)ions and HCO3-Hydrogen bicarbonate) ions .The H+ ions is responsible for decrease in pH or making the water acidic in nature. The bicarbonate is further divided into H+ ions and carbonate ions. This further addition of H+ ions leads to further decrease in the pH of the solution. The vacant carbonate ions react with calcium carbonate. This is Bjerrum effect.
2) The ocean has large amount of carbonate ions and the distillated water don't contains carbonate ions . Therefore ,when the CO2 is added to the distilled water, it reacts with the water and leads to the formation of large amount of H+ ions. The carbonate that is present in the sea water in large amount or the high concentration of salt tends to bind with the H+ ions in the water and leads to the further increase in pH .This process is to maintain the pH of water and is known as Alkalisation effect in sea water .

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