Simple 2-part question - heating water

14a) Should you install a solar water heater? The average home has a 200 liter hot-water tank, which is effectively drained and replenished three times per day. Assume that the entering tap water is 19 degrees Centigrade and is heated to 53 degrees Centigrade. Given an average energy from sunlight of 1.53 kJ/cm2 per day, how large would the collection area (in m2) of a solar water heater need to be if its efficiency is 30%? Assume that the price of a solar collector is $375/m2. How much would it cost to install this hot water system?

Rate of destruction of methane

At an altitude of about 35 kilometers, the average concentrations of O* and of CH4 are approximately 100 and 1E11 molecules cm-3 respectively, and the rate constant k for the above reaction is approximately 3.4E-10 cm3 Molecules-1 s-1. Calculate the rate of destruction of methane in molecules per second per cubic centimeter.

Dissolved oxygen question

29) A groundwater sample , at 25 degrees C, has Eh= 1.00 and the pH=6.800. When the system is at equilibrium, calculate the amount ofdissolved oxygen (in ppm) in the ground water sample.

Short equilibrium question

#29b) At a pH of 6.0 and pE 3.0, what's the concentrationn of Fe2+ (in mol/L) in equillibrium with Fe(OH)3? Hint from instructor in email: Use the Nernst equation and the Ksp for the solubility of solid iron (III) hydroxide.

Electricity generation in kwH

21) Assume a wind turbine w/ a hub 50m above ground, a rotor diameter of 25m, and a wind conversion efficientcy of 25 percent. The turbine operates in an area w/ an average windpower density of 600 watts/sq meter at 50m altitude. How much electricity (in kwH) can the turbine generate per year?Wind densities greater than or equal to 500 watts/sq meter at an altitude of 50m are present on 1.3 percent of the land area of the USA. If, on average, wind farms contain 8 turbines/sq km, how much electricity (in kwH/yr) could be generated from these wind turbines? (The area of the USA is 7,827, 989 sq km).