(a) In a chemical reaction a solid decomposes to form two different gases. Would
ID: 945362 • Letter: #
Question
(a) In a chemical reaction a solid decomposes to form two different gases. Would you expect DS to be positive, negative, or close to zero for this reaction?
DS for this reaction should ---Select--- be positive be negative be close to zero .
(b) In which of the processes described below should the entropy increase? Choose all of the correct possibilities.
ice cubes melting at -5 oC and 1 atm pressure
water disappearing from a tea kettle by boiling away
gas sprayed onto a cold surface deposits (solidifies) and becomes part of the surface
dissolution of sugar in a hot cup of coffee
some dry ice left on a tabletop disappearing via sublimation
Explanation / Answer
a) positive.
solid -------------> gas + gas
here gas has more disorder than solid particles. so entropy increases. positive.
b)
a) ice cubes melting at -5 oC and 1 atm pressure
b) water disappearing from a tea kettle by boiling away
c) dissolution of sugar in a hot cup of coffee
d) some dry ice left on a tabletop disappearing via sublimation
these all four cases, disorder of molecules increases. so entropy increases.
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