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# Will the copper concentration be below the toxic level

An electric water heater held at 140 degrees F is kept in a 70 degree F room. When purchased, its insulation is equivalent to R 5. An owner puts 25-ft^2 blanket on the water heater, raising its total R value to 15. Assuming 100% conversion of electricity into heated water, how much energy (kWhr) will be saved each year? if electricity costs 8.0 cents/ kWhr, how much money will be saved in energy each year?

I believe its q=A(T2-T1)/R, but don't know the area

One day, you are out hiking and find a beautiful river where you want to go fishing. The river is flowing at 1.5m/s. Next to the river, there is an abandoned mine leaching copper in the river at a concentration of 14mg/L. Copper is toxic to fish at concentrations above 1.0mg/L. Fortunately, copper precipitates out of the water as river flows downstream, which can be considered second order decay, with k=1.2Lmg-min.
If you are downstream 50 meters from the mine, will the copper concentration be below the toxic level, so that you can go fishing? Model the river as a plug flow reactor and assume that steady state conditions apply

I believe its 2nd order so -kc^2=1/Con.out=1/Con.in+kt

#### Solution Preview

Problem 1 :
Without blanket
Q = A/R [ (T2-T1)t ]
Here A = 25 ft square = 25 * 12 * 2.54 cm square = 762 cm square 0.0762 metre square.
R = 5
T2-T1= 140 -70 = 70F
t = 1 year = 365 * 24 = 8760
energy saved in 1 year = [762 * 70 * 876] / 5 = 96451380 watts / hr = 93451.380 k w hr

withblanket
Q = A/R [ (T2-T1)t ]
Here A = 25 ft square = 25 * 12 * 2.54 cm square = ...

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