Had my first chemistry exam today. This was entirely too easy of test to do as poorly as I did. I definitely did not study sufficiently this week as I’ve been distracted by physical therapy and getting the biomechanics on my race bike dialed in. Here is a sample question from today’s exam:

A 450.0g piece of iron (sFe = 0.473J/gºC) was heated to 275ºC and put into 650g of water.  If the final temperature of the mixture was 45.0ºC, what was the initial temperature of the water?

For this problem you need to have committed a comonly used formula to memory.

mFe*sFe*(Tf- TiFe) + mw*sw*(Tf – Tiw) = 0

Basically matter or “m” of iron (symbol Fe) times specific heat or “s” of iron times (final temperature minus (-) intiail temperature) or what is called change in temperature (delta t)

Plus (+)

matter of water etc. etc. So Fe being iron w being water.

We then work the problem out algebraically inputing the known values from the question into the forumla

450.0g(0.473J/gºC)(45.0ºC -275ºC) + 650g(4.184J/gºC)(45.0ºC – Tiw) = 0

212.9J/ºC(-230ºC) + 2720J/ºC(45.0ºC – Tiw) = 0

-48970J + 12200J – (2720J/ºC) Tiw = 0

73400 J  =  (2720 J/ºC) Tiw

Tiw = 27ºC