Hydrothermal vents deep on the ocean floor spout water at temperatures as high a
ID: 1507858 • Letter: H
Question
Hydrothermal vents deep on the ocean floor spout water at temperatures as high as 530°C. This temperature is below the boiling point of water because of the immense pressure at that depth. Since the surrounding ocean temperature is at 4.0°C, an organism could use the temperature gradient as a source of energy
(a) Assuming the specific heat of water under these conditions is 1.0 cal/g·°C, how much energy is released when 5.0 L of water is cooled from 530°C to 4.0°C
(b) What is the maximum useable energy an organism can extract from this energy source? (Assume that the organism has some internal type of heat engine acting between the two temperature extremes.)
(c) Water from these vents contains hydrogen sulfide (H2S) at a concentration of 0.65 mmole/liter. Oxidation of one mole of H2S produces 310 kJ of energy. How much energy is available through H2S oxidation of 5.0 L of water?
Explanation / Answer
a)
Q = m*c*delta T
Q = density*volume*c*delta T
Q= 1000 kg/m3 * 0.005*1cal/10^-3 * 526
Q = 2.63 Cal
b)
Efficiency = 1-T2/T1 = 1- (277/803) = 0.655
Maximum useable energy = 2.63 cal*0.655
Maximum useable energy= 1.72 Cal
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