The first law of thermodynamics states________? The total energy of the universe
ID: 1058765 • Letter: T
Question
The first law of thermodynamics states________? The total energy of the universe is constant. Delta H_rxn^o = sigma n delta H^o f(products) - sigma m delta H^o f(reactants) For any spontaneous process, the entropy of the universe increases The entropy of a pure crystalline substance at absolute zero is zero For an isothermal process, delta S_system = _________ - delta H_sys (delta H_sys)(T) -(delta H_sys)/(T) q + w The entropy of a reversible system, delta S_system, can be________ positive negative zero positive, negative, or zero Without calculating entropy, evaluate which reaction shows a decrease in the entropy. CaCO_3(g) rightarrow CaO(s) + CO_2(g) 2C(g) + O_2(g) rightarrow 2CO(s) CO_2(s) rightarrow CO_2(g) 2H_2O(t) rightarrow 2H_2O(g) Which of the following is a reversible process? Melting of ice at a constant temperature of 25 degree C at latm. Evaporation of water at a constant temperature of 25 degree C and latm. Freezing of gaseous water at a constant temperature of -100.0 degree C and latm. Boiling of liquid water at a constant temperature of 100.0 degree C and latm.Explanation / Answer
1. First law of thermodynamics is about law of conservation of eneergy. It states that energy can neither be created nor destroyed. It can be changed from one form to another. A is correct.
2. isothermal process is either to do with change of liquid to vapor or solid to liquid during wihch either heat is added ay constant temperature. hence deltaH/T = entropy change of system
3. for a reversbile process there is no change in entropy. So entropy change is zero.
4. entropy is degree of disorder. Higher the degree of disorder, higher the entropy. the entropy of solids is less than liquid which in turn is less than gases. Entorpy decreases when a gas becomes a solid. Hence in the second reaction 2C(g + O2(g) ---->2CO(s), entropy decreases.
5. Reversible process refers to those process in which we initial step can be brought about by by changing the external condition infinitesimally; Accordingly, melting of ice at constant temperature of 25 deg.c and 1 atm is reversible. Evaportation is also reversible. Freezing is reversiblele abd boiling of liquid water is also reversible.
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