Posted: November 18th, 2015

Ocean Ossification

Ocean Ossification

Determine the best answers for the questions below. Always round appropriately.

1. Carbon dioxide and water combine to form carbonic acid. Carbonic acid in seawater negatively impacts

oceanic environments. Acidified seawater can theoretically be neutralized through the addition of a base.

One such base is calcium hydroxide. What products would be formed in the neutralization of carbonic acid

with calcium hydroxide? In Canvas, type subscripts as full-size numbers. Don’t include symbols or

coefficients but pay attention to them below.

H2CO3 (aq)     +       Ca(OH)2 (aq)  –à    (s) +    2      (l)

2. Scientists estimate that 2 x 1016 g of calcium hydroxide would be required per year to counteract the

effects of modern CO2 emissions (see equation below). This amount is impractical, but it suggests something

about the rate at which CO2 is absorbed into the oceans. How many grams of CO2 are absorbed by the world’s

oceans per year?

CO2 (g) +    Ca(OH)2 (aq) -à    CaCO3 (s) +   H2O (l)

_______ g CO2 year/year

3. Your answer above should have units of g CO2 per year. To give you a better sense of this number, convert

it to tons per hour. (1 ton = 2000 pounds exactly) (1 pound = 454 g) (there are two more unit factors you

need to come up with on your own)

Based on your answer, which of the following correctly completes the statement below?

Oceans absorb an estimated ___________ tons of CO2 per hour.

one billion      one million         ten thousand        one thousand      one hundred

4. Kurt House, a research fellow at MIT, was recently recognized for his novel strategy to counter ocean

acidification. His idea is to use the sodium chloride in seawater to produce sodium hydroxide (a base),

which could then be reintroduced to neutralize increased levels of carbonic acid. The equation to produce

sodium hydroxide is shown below…

NaCl (aq) +    H2O (l)    —-à      NaOH (aq) +    HCl (aq)

In a scaled-down version of his process, 1.0 kg of seawater is used. This amount contains 966 g of water

and 29.5 g NaCl.

a.       How much NaOH (aq) should be produced if the reaction gives 100% yield? Give your answer in grams.

b.      Which reactant is the “limiting reactant” in Question 4a?

Choose one ——->  NaCl   H2O   NaOH     HCl

c.       Suppose only 15.6 g of NaOH are actually produced…

What is the percent yield of the scaled-down reaction?

77.2%      0.729%          72.9%          0.722%          over 100%

5. Another idea put forth to counteract ocean acidification is massive restoration of the oceans’ sea grass beds1 . New research indicates that sea grass does a better job of removing and sequestering CO2 than do

dense forests. Sea grass absorbs CO2 to support its photosynthetic processes…

CO2 (g) +     H2O (l) ——>    C6H12O6 (s) +     O2 (g)

Suppose you’re testing a newly-discovered species of sea grass that exhibits good tolerance of elevated ocean temperature. Under STP conditions, the sea grass specimen emits 1.62 L of oxygen gas. What mass of CO2 was absorbed and reacted to produce this amount of product? Give your answer in grams.

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