1) Delta s is positve for the reaction_________________

a) 2H2(g) +O2(g) yields 2H2O(g)

b) 2NO2 (g) yields N2O4(g)

c) CO2(g) yields CO2(s)

d) BaF2(s) yields Ba+2(aq) +2F^-(aq)

e) 2Hg(l) +O2(g) yields 2HgO(s)

2) The Ksp for CaF2 is 3.9 x10^-11 at 25 degrees celsius what is the molar solubility of [Ca^+2]?

3) What is the cathode in the hydrogen fuel cell?

a) O2

b) Li

c) Pt

d)KOH

e) H2

please refer to explanation

Step-by-step explanation

1) You have to determine the ΔS of each reaction. For this, use the following equation. The ΔS values you can find in thermodynamic tables.

ΔSrxn = ΔSprod - ΔSreactants

a) 2H2(g) +O2(g) --> 2H2O(g)

ΔSrxn = 2*188.83 - [(2*130.68 )+(205.14 )]

ΔSrxn = -56 J/mol

b) 2NO2 (g) ---> N2O4(g)

ΔSrxn = 304.29 -2(240.06 )

 ΔSrxn = -175.83 J/mol

c) CO2(g) --> CO2(s)

 ΔSrxn = 51.11 -213.74 

 ΔSrxn = -162.63 J/mol

d) BaF2(s) --> Ba⁺²(aq) +2F^-(aq)

 ΔSrxn = 2*-13.8 + 9.6 - (96.4)

ΔSrxn = -114.4 J/mol

e) 2Hg(l) +O2(g)---> 2HgO(s)

ΔSrxn = 2*70.29 -[2*76.02 + 205.14]

ΔSrxn = -216.6 J/mol

None of the given reactions have a positive entropy change. All of them go from a state of higher energy to a state of lower energy.

2)

CaF2 --> Ca²⁺ + 2F^-

___x_______x______2x

Ksp = [Ca²⁺][F^-]²

3.9x10^-11 = (x)(2x)²

3.9x10^-11 =4x³

x = 2.1x10^-4 M

3) a) O2