molar heat capacity?

Question

A coffee cup (or constant pressure) calorimeter contains 108.0 g of water at an initial temperature of 25.0°C. 118.7 g of tin metal at a temperature of 100°C is added. The final temperature in the calorimeter is 29.2°C. What is the molar heat capacity of the tin? The molar heat capacity of water is 75.4 J/(mol•°C). Assume that the heat capacity of the coffee cup is negligible.

Answer 1

So 108 grams of water increased 4.2C. 108g / 18g/mole = 6 moles water

75.4 L/mol-C x 6 moles x 4.2 C = 1900 J

The 1900 Joules all came from the Tin which dropped in temperature 100-29.2=70.8C

A mole of tin is 118.69 so you have one mole of it.

1900 J/70.8C/1mole = 26.8 J/(mol-degreeC) molar heat capacity of tin.

Which is right, I looked it up as 27 J/mol-C.

Answer 2

Well the equation to use here is easy Q = moles x delta(Temperature) * c mass = 1.2 g delta(T) = 1.0 x 10^12 K Q = 63 J To convert mass to moles, you need to know the molecular mass Since diamond is simply carbon, the molar mass is 12 g/mol So in our sample we have 1.2 g C (1 mole C/ 12 g C) = 0.1 moles C So now we use Q = nTc (63 J) = (0.1 moles)*(1.0*10^2 K) * molarc molar c = 6.3 J/(mol*K) which is the same as 6.3 J/(mol*C)