Question

A sample of water was placed in a refrigeration device and the temperature was gradually lowered. the sample become super cooled, and did not freeze until the temperature reached -20 ^oC, which of the following statements is correct:

A

ΔS(sys) > 0, ΔS(sourr) = 0, ΔS(total) > 0

B

ΔS(sys) > 0, ΔS(sourr) > 0, ΔS(total) > 0

C

ΔS(sys) < 0, ΔS(sourr) > 0, ΔS(total) > 0

D

ΔS(sys) < 0, ΔS(sourr) > 0, ΔS(total) < 0

Answer 1

Assume:

dSsystem = water

dSurroundings, all other stuff

dSuniverse --> dSsystem +dSurroundings

since this is actually ocurring,t hen

dSunvierse > 0, for any possible process

since T is decreasing, then

dSwater --> must decrease, since dS is functino fo T

dS water < 0

dSsurroundings --> must increase, since water is giving OFF its heat, so dSurronudings must incerase

dSurr > 0

dSsys < 0

dStotal > 0

ignore D, since dStotal < 0

ignore A and B sicnce dS > 0

therefore

ΔS(sys) < 0, ΔS(sourr) > 0, ΔS(total) > 0