Chemistry Help(Calorimetry)
posted by Bonn on .
I have a few questions to ask, since I was absent from school and I do not really understand the calorimetry problems.
1) When a 16.9 g sample of NaOH dissolves in 70.0 g of water in a calorimeter, the temperature rises from 22.4*C to 86.6*C. Calculate for Delta H for the process NaOH(s) > Na(aq) + OH(aq)
2) A 2.5 g sample of zinc is heated, then placed in a calorimeter containing 65.0 g of water. Temperature of water increases from 20.00*C to 22.50*C. The specific heat of zinc is 0.390 J/g*C. What was the initial temperature of the zinc metal sample.

1).
q = Mass H2O x specific heat H2O x delta T
delta H = q/16.9 grams if you want it in Joules/g and that time molar mass NaOH if you want it in Joules/mole.
2)heat lost by Zn + heat gained by water = 0
[mass Zn x specific heat Zn x (TfinalTinitialZn)] + [mass water x specific heat water x (TfinalTinital)] = 0
Solve for Tinitial Zn 
the number of calories needed to raise the temperature of 100 grams of water 10 degrees Celsius is the same as the number of calories needed to raise the temperature of 1,000 grams of water what amount?

Convert 34.5 in2 to cm2. Report the answer to the correct number of significant figures. (1 inch = 2.54 cm is an exact or defined conversion.)

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