Question

When the power supplying a 30.0 gallon water heater was turned off, the temperature dropped from 75.0 degrees celsius to 22.5 degrees. How much heat was lost to the surrounding?

I know I need to find the energy and or heat lost, but how will i get the mass of H2O used to complete the equation?

Answer 1

Don't we assume that if it is a 30 gallon water heater that it will be full of H2O so it will hold 30 gallons. 1 gallon = 3.785 L.

Answer 2

I could multiply 30 by 3.785 L to find the volume, but to find the mass of water used I also need the density of the water which is not given. Is there a different equation I should be using other than...
qH2O = mH2O x CsH2O x delta T ?

Answer 3

No. Density is water generally is 1.0 g/mL for most of these problems. Therefore, volume in mL = mass in grams.

Answer 4

Okay, thank you for clarifying. :)