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# Density, Conductivity, Coal-Combustion Calculations

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Question 15: The density of liquid water at 0 degrees C is 0.9987 g/cm cubed; the density of ice at this same temperature is 0.917 g/cm cubed.

a. Calculate the volume occupied at 0 degrees C by 100. g of liquid water and by 100. g of ice.
b. Calculate the percentage increase in volume when 100. g of water freezes at 0 degrees C.

Question 19: Predict what will happen when each of these dilute solutions is tested for conductivity. Please explain to me why you made your predictions.

a. CaCI2 (aq)
b. C2H5OH (aq)
c. H2SO4 (aq)

Question 23. A coal-burning power plant generates electrical power at a rate of 500 megawatts; that is, 500 X 10 to the 6th power per 5.00 X 10 to the 8th power joules per second. The plant has an overall efficiency of 0.375 for the conversion of heat to electricity. Assuming the power plant burns coal that releases 30 kJ/g, calculate the mass of coal (in grams and metric tons) that will be burned in 1 year of operation (1 metric ton = 1 X 10 to the 3rd power kg = 1 X 10 to the 6th power g).

https://brainmass.com/chemistry/bonding/density-conductivity-coal-combustion-calculations-13079

#### Solution Preview

15. This is a basic math problem. Density is merely mass/unit volume or D = M/V
In this setup we know D and M
For water: D = 0.9987 g/cm3 and M = 100g
For ice: D = 0.917 g/cm3 and M = 100 g
Using rearrangement to isolate the unknown "V" we get V = M/D
(multiply both sides by V and divide both by D)
So for water V = 100g / 0.9987 g/cm3 = 100.1302 cm3
and for ice V = 100g / 0.917 g/cm3 = 109.0512 cm3

19. a) CaCl2is an ...

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