In a cylindrical water tube of length 4 cm and radius 6 mm, at t=0 s, the concentration of
mole
molecules of oxygen changes from 0.5
m3
mole
to 0.1
across the tube.
If the diffusion constant of oxygen inside water
is 8x 10-10 m2
find:
S
The number of mole of oxygen going from the
higher concentration to the lower concentration
every second
n =
v mole

The heater element of a 120 v toaster is a 5.4 m length of nichrome wire, whose diameter is 0.48 mm. the resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10-6 ω·m. the toaster is operated at a voltage of 120 v. (a) what is the power drawn by the toaster? (b) if the cost of electricity is 12 ¢ per kilowatt-hour, and it takes 2 minutes to toast bread, how much does it cost for toasted bread? (c) when the heater element is at room temperature, is the resistivity in the nichrome wire greater than, less than, or equal to it’s resistivity when at operating temperature? explain.