Thermodynamic values are given in the appendix section of any general chemistry

Question

Thermodynamic values are given in the appendix section of any general chemistry textbook. i. Wi ithout using an appendix, predict the sign. or-) of the entropy change, as, for each of the following reactions: H2O(g) H2O(1) C6H6(aq) C6H6(g) KCI(aq) KCl(s) 2H20(1) 2H2(g)+O2(g) 2c6H6(g) 15029) 12 co2(G)6 2) i. Without using an appendix, circle the compound in each set (row) that should have the greatest value of entropy. Explain your overall reasoning below C3H8(g)-- Li20(s) Cacl2(s) C2H6(g) LiBr(s) CH4(g) Li3N(s) Consider the reaction. 6CO2(g) + 6H20(1) C6H1296 (s) . 602 (9) Calculate 6" for the reaction under standard conditions using the equation AG, AH, TAS iii. b. Is the above reaction spontaneous in the forward direction under standard conditions? How do you know? industry at a temperature of 1000 °C. If high temperature is not necessary to make the reaction spontaneous, then why might the high temperature be used? iv. The following reaction for the production of hydrogen cyaride is spontaneous under standard conditions, but is normally performed in 2HCN(g)" 6H20(g) 2NH3(g) . 302(g)" 2CH4(g)

Explanation / Answer

Entropy is a measure of chaos; therefore, the more chaotic it becomes, the more entropy increases.

In general:

Entropy increases with the number of particles/moles in the system:

1 mol of AB has less entropy than 1 mol of A and 1 mol of B; due to higher amount of microstates

Entropy increases as the volume of particles increases. This can be compared with physical states

Volume of Solid < Volume of Liquid << Volume of Gas

Therefore, Gases have higher entropy than liquids and solids. Liquids have higher entropy than solids.

As T increases, the entropy increases, by definition, since it is a state function which depends on Temperature.

Mixture typically increases Entropy, so ordered states get higher amount of microstates.

Example could be Gas A + Gas B separated by a membrane, then eventually mixing A + B, microstates increases, meaning that entropy increases

a)

H2O from gas to liquid, decrease entropy, due to organization in system

b)

C6H6 --> C6H6

gas is much more chaotic than aqueous solution, therefore, increase in entropy

c)

KCl(aq) --> KCl(s)

this increase in entropy, since aqueous is less organized than KCl

d)

2 mol of liquid forms 2+1 = 3 mol of gases, therefore, increase in gas/chaos/entropy

e)

this is combustion, 2+15 = 17 molecules of gas form 12+6 = 18 moelcules

then, increase in chaos/entropy

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