AP Environmental Science 9.H Ocean Acidification

[Maximum number: 7]

The graph shows measurements of atmospheric levels of carbon dioxide ( $\mathrm{CO}_{2}$ ) at Mauna Loa Observatory, Hawaii, and the measurements of pH levels in the ocean nearby at Station ALOHA. Measurements of pH began in 1992.

ATMOSPHERIC CARBON DIOXIDE AT MAUNA LOA AND OCEANIC pH AT STATION ALOHA, HAWAII

(a)

Use the graph above to answer the following questions.

[ 1 ]

(i)

Determine the pH recorded at Station ALOHA in 2005.

[ 1 ]

(b)

Changes in atmospheric carbon dioxide affect Earth's oceans.

[ 4 ]

(i)

Predict the effect of increased concentration of atmospheric $\mathrm{CO}_{2}$ on the concentration of $\mathrm{CO}_{2}$ in the ocean.

[ 1 ]

(1 point for correctly predicting the effect of an increase in concentration of $\mathrm{CO}_{2}$ in the ocean)

- Oceanic $\mathrm{CO}_{2}$ will increase.

- Dissolved oceanic $\mathrm{CO}_{2}$ will increase.

(ii)

Based on the data, identify the relationship between the concentration of atmospheric $\mathrm{CO}_{2}$ and the pH of ocean water.

[ 1 ]

Based on the data, identify the relationship in the concentration of atmospheric $\mathrm{CO}_{2}$ and the pH of the ocean water.
(1 point for correctly identifying the relationship between the concentration of atmospheric $\mathrm{CO}_{2}$ and the pH of ocean water based on data)

- As atmospheric $\mathrm{CO}_{2}$ increases, pH decreases.

- As more $\mathrm{CO}_{2}$ dissolves in the water, it becomes more acidic/less alkaline.

- As atmospheric $\mathrm{CO}_{2}$ increases, $\mathrm{H}_{3} \mathrm{O}^{+}$ or $\mathrm{H}^{+}$ ions increase.

(iii)

Provide the complete chemical equation that represents the reaction between oceanic carbon dioxide $\left(\mathrm{CO}_{2}\right)$ and water $\left(\mathrm{H}_{2} \mathrm{O}\right)$ .

[ 1 ]

(l point for the correct balanced chemical equation that represents the reaction between oceanic carbon dioxide and water)

- $\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{H}_{2} \mathrm{CO}_{3}$ (carbon dioxide plus water produces carbonic acid)

- $\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{H}^{+}+\mathrm{HCO}_{3}{ }^{-}$ (carbon dioxide plus water produces one hydrogen ion and one

bicarbonate ion)

- $\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{H}^{+}+\mathrm{CO}_{3}{ }^{2-}$ (carbon dioxide plus water produces two hydrogen ions and one

carbonate ion)

(iv)

Identify the specific environmental problem that directly results from the decrease in pH of Earth's oceans.

[ 1 ]

(c)

Changes in pH in the world's oceans pose a risk to many marine organisms.

[ 2 ]

(i)

Explain why certain organisms, in particular those with calcium carbonate shells or exoskeletons, are threatened by the decreasing pH levels measured in seawater.

[ 2 ]

AP Environmental Science Stb 4 H Explain the Causes and Effects of Ocean Acidification Questions

Exam points

AP Environmental Science Stb 4 H Explain the Causes and Effects of Ocean Acidification Questions question 1

Question (a)

Question (i)

Question (b)

Question (i)

Question (ii)

Question (iii)

Question (iv)

Question (c)

Question (i)