Tutorial Problems 1

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Tutorial Problems 1

1) The normal boiling point of liquid oxygen is –182.97

o C. What is this temperature on the Kelvin scale ? 2) Suppose a constant-volume gas thermometer has a pressure of 1.5 x 10 4 Pa at the triple point of water and a pressure of 1.95 x 10 4 Pa at some unknown temperature T. What is T ? 3) A sample of gas at 20 o C has a volume of 0.6L at a pressure of 0.8 atm. Find a) the number of moles b) the number of molecules. (1L = 1Litre = 1000cm 3 ). 4) Two moles of helium gas are at 20 o C and a pressure of 200kPa. (a) Find the volume of the gas. (b) If the gas is heated to 40 o C and its pressure reduced by 30 %, what is the new volume ? 5) When 400 J of heat are supplied to 150g of a liquid, its temperature rises by 2.5K. What is its specific heat. 6) During a bout of flu, an 80 Kg man ran a fever of 2 C o above normal, that is, a body temperature of 39 o C. To raise his temperature by that amount, his body had to produce extra heat by means of chemical reactions in his cells. Assuming the human body is mostly water, how much heat was needed ? 7) a) A home owner in a cold climate has a coal burning furnace that burns 9000 Kg of coal during a winter. The heat combustion of coal is 2.5 x 10 7 J.kg

-1 . If 15% of the heat is lost up the chimney, how many joules were actually used to heat the house.

b) The home owner proposes to install a solar heating system, heating large tanks of water by solar radiation during the summer and using the stored energy for heating during the winter. Find the required dimensions of the storage tank, assuming it to be a cube, to store a quantity of energy equal to that computed in part (a). Assume that the water is raised to 49 o C in the summer and cooled to 27 o C in the winter.

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