An average hot water tank will hold 300.0 L of water needs to be kept at 65.0C in order to kill any bacteria in the water. If you are filling a new tank with water at a starting temperature of 12.5C, what mass of natural gas

Question

(methane) must be burned in a complete combustion reaction in order to bring your tank up to the correct temperature?

I think I mostly need help with identifying the equation needed to solve this but if anyone is able to fully explain it, it would be greatly appreciated

Answer 1

You have three problems here.
1. First you need to determine how much heat is needed to raise the temperature of 300.0 L of water at 12.5 C to a final temperature of 65 C.
2. Then you need to write the equation for the combustion of methane and calculate how much heat 1 gram of methane (or some other quantity) produces. Then you can calculate how many grams of methane are needed to produce what you need in #1.
3. You DON'T have the heat produced from the combustion of methane. I don't know if you didn't have that in the problem or if you just didn't type it in. I assume also that the specific heat of water is given or you know it and that you know the density of water at that temperature is 1.00 g/mL.

#1. q = heat needed = mass H2O x specific heat H2O x (Tfinal - Tinitial)
q = 300,000 g x 4.184 J/g*C x (65.0 - 12.5) = approximately 66,000,000 J or 66,000 kJ. You should confirm this.
#2. CH4 + 2O2 ==> CO2 + 2H2O
I looked up the heat of combustion for CH4 on th web and found 889 kJ/mol CH4. You should use the value in your text/notes/discussions in class. So 889 kJ/mol is 889 kJ/16 g CH4. You want 66,000 kJ from part 1 and you have reaction in part 2 that will produce 889 kJ/16 g. So
16 g CH4 x 66,000 kJ/889 kJ = ? g CH4.
Hope this helps. Post your work if you get stuck.

Answer 2

Thank you DrBob222, really appreciate it!