Please help by answering all of the listed problems...Not Just one of them !!! 1
ID: 1877440 • Letter: P
Question
Please help by answering all of the listed problems...Not Just one of them !!!
1.The temperature of an object is changed when heat is added to or extracted from it. Determine the final temperature (in °C) of a 90.0 g mass of brass initially at 64.0°C if 1,200 J of heat energy is extracted from it. The specific heat of brass is 380 J/(kg · °C).
2.Steam at 100°C is condensed into a 46.0 g steel calorimeter cup containing 220 g of water at 21.0°C. Determine the amount of steam (in g) needed for the system to reach a final temperature of 56.0°C. The specific heat of steel is 490 J/(kg · °C).
3.Determine the amount of work done on an ideal gas as it is heated in an enclosed thermally isolated cylinder topped with a freely moving piston. The cylinder contains of n moles of the gas and the temperature is raised from T1 to T2. The piston has a mass m and a cross sectional area A. (Use any variable or symbol stated above along with the following as necessary: R.)
4.A thermodynamic system undergoes a process in which its internal energy decreases by 485 J. Over the same time interval, 204 J of work is done on the system. Find the energy transferred from it by heat.
Explanation / Answer
a) Q = m C delta T
1200 = 90 x 10^-3 (380) (64-T)
Final Temp = T = 64- 3.51 = 60.49 C apprx
b) let the mass of steam = m kg
m (2.26 x 10^6 J/kG) + m ( 100- 56)( 4190 J/kg C) = 220 x 10^-3 ( 56-21) ( 4190) + 46 x 10^-3 ( 56-21) 490
m ( 2444360 ) = 32280;15
m = 13.21 gm of steam is required
c) For a tehrmally solated cylinder, as heat is supplied, the gas wiull expand and pressure will rmaon constant
W = P delta V = nR delta T = nR ( T2-T1)
W = FA delta V
where F is tfe force exerted on poiston = mg
A= area = cross sectional area
W = mgA delta V = nR ( T2-T1)
Both the expressions give teh work done on the gas
d) Q = -U + W ( as per first law)
Q = -485 +204 = -281 J
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