During the isothermal heat addition process of a carnot cycle, 900 kj of heat is added to the working fluid from a source at 400oc. what is the entropy change of the working fluid? what is the entropy change of the source? what is the total entropy change for the process? [

the entropy change of the fluid during the process process is is 1.337 kJ/K, the change for the source is -1.337 kJ/K and the total entropy change is 0

Explanation:

since the Carnot cycle is a reversible cycle, the entropy change is related with the heat exchanged through:

ΔS =∫dQ/T

since the temperature remains constant

ΔS =∫dQ/T=(1/T)*∫dQ = Q/T

Q= heat added to the system

T= absolute temperature = 400°C= 673 K

therefore

ΔS = Q/T = 900 kJ/ 673 K = 1.337 kJ/K

ΔS working fluid = 1.337 kJ/K

since the process is reversible, the entropy change of the universe (total entropy change)  is 0 (there is no entropy generation). thus

ΔS universe = ΔS working fluid + ΔS source = 0

ΔS source= -ΔS working fluid = -1.337 kJ/K

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.