Specific heat/ phase change problem….? [look inside]?
what did i do wrong? can you show me the correct steps?
thanks
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PROBLEM
how many joules are required to heat 75 grams of water from -85°C to 185°C? The heat capcity of steam is 1.84 J/g °C…
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i used
q= mCp∆T
(75g)(185-(-85)) (1.84 J/ g °C)
and i got 37,260 J… but the teacher said it was 250.9 kJ..
and when i converted my answer to kJ (just divide by 1000), i still didn’t get the right answer.
There are several different heat capacities that you must use for this calculation.
1. Calculate the energy to warm the ice (solid water) from -85 to 0 C.
You must use the specific heat for ice, multiplied by the mass and the total temperature rise.
2. Calculate the required energy to melt the ice.
3. Calculate the energy to warm the liquid water from 0 to 100 C
4. Calculate the energy required to heat the steam from 100 C to 185 C.
The total energy required is the sum of 1 + 2 + 3 + 4.
Sp Ht Tables (how to use) – Solving p. 495 #4 on Specific Heat – Part 3