Work Book IV Thermodynamics Questions) 1) The entropy will usually increase when

Question

Work Book IV Thermodynamics Questions) 1) The entropy will usually increase when L a molecule is broken into two or more smaller mol IL a reaction occurs that results in an increase in the number of moles of gas. III. a solid changes to a liquid. IV. a liquid changes to a gas. (a) I only (b) II only (c) III only (d) TV only (e) L II, III, and IV ANSWER 1 2). Which statement is incorrect? (a) At constant pressure, AH- AE PAV (b) The thermodynamic symbol for entropy is S. (c) Gibbs free energy is a state function. (d) For an endothermic process, His negative. (e) If the work done by the system is greater than the heat absorbed by the system, E is ANSWER 2 3. A system suffers an increase in internal energy of 80 Jand at the same time has 50 J of work done on it. What is the heat change of the system? ANSWER 3:

Explanation / Answer

(1) Entropy is the measure is the measure of disorderness. More is the disorderness more is the entropy.

So, in all the four cases given the disorderness will increase, so entropy also increases.

So the answer is (e)

(2)

(d) is incorrect.

Because for an endothermic reactions since heat is added to the system, H is taken as positive.

(3) According to first law of thermodynamics,

change in internal energy = q + w

80 = q + 50

q = 30 J

(4) Amount of heat absorbed by water = m * s * (t2 - t1)

q = 4000 * 4.184 * (29.765 - 24.000)

q = 96483 J

This amount of heat has been released from the combustion of methanol

Moles of methanol used = mass / molar mass = 5.000 / 32 = 0.156 mol

SO, change in enthalpy = q / n = 96483 / 0.156 = 618481 J/mol = 618.481 kJ/mol

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