Enthalpy is favored when...
H < 0
Entropy is favored when...
S > 0
When the S universe is positive then the reaction is ____ favored
product
2NO(g) + 2H2(g) N2(g) + 2H2O(l) for which Ho = -752.2 kJ and So = -351.6 J/K at 298.15 K.
(1) Calculate the entropy change of the UNIVERSE when 2.175 moles of NO(g) react under standard conditions at 298.15 K.
(2) Is this reaction reactant or product favored under standard conditions?
(3) If the reaction is product favored, is it enthalpy favored, entropy favored, or favored by both enthalpy and entropy? If the reaction is reactant favored choose 'reactant favored'
2361
product
enthalpy
If a lower temp is required to reach the same vapor pressure as another molecule, then the first molecule have _____ IMF
weaker
For silicon, Si, the heat of fusion at its normal melting point of 1410oC is 46.4 kJ/mol. The entropy change when 2.23 moles of liquid Si freezes at 1410oC, 1 atm is
-61.5
equilibrium phase change formula
Sphase = Hphase/Tphase
The molar solubility of manganese(II) hydroxide in a 0.159 M manganese(II) nitrate solution is
2.7E-7
Ksp equation
[x][y]
If a chemical reaction occurs in a direction that has a positive change in entropy then
disorder increases
If H < 0 and S > 0 then...
always spontaneous
If H < 0 and S < 0 then...
spontaneous at low temp
If H > 0 and S > 0 then...
spontaneous at high temp
If H > 0 and S < 0 then...
never spontaneous
trend of molecule size, attractive forces, and entropies
As a molecule gets bigger, the attractive forces decrease
As the attractive forces decrease, the entropies increase
As the molecule gets bigger, entropies increase
how to calculate new pressure at new volume
P2 = (V2/V1) x P1
vapor will condense if...
it is more than the given pressure
ex: P > 100mm Hg
From the following vapor pressure data for pentane, an estimate of the molar heat of vaporization of C5H12 is
P, mm Hg T, Kelvins
100. 260
400. 292
27.3
Consider the insoluble compound silver hydroxide, AgOH. The silver ion also forms a complex with ammonia . Write a balanced net ionic equation to show why the solubility of AgOH(s) increases in the presence of ammonia and calculate the equilibrium constant for this reaction.
For Ag(NH3)2+, Kf = 1.6E+7
AgOH(s) + 2NH3(aq) --> Ag(NH3)2+(aq) + OH-(aq)
0.32 (knet = Ksp x Kf)
processes that release energy & the phase changes associated
gas --> liquid: condensation
gas --> solid: deposition
liquid --> solid: freezing
A student determines the value of the equilibrium constant to be 2.57E-25 for the following reaction.
CH4(g) + H2O(g) 3H2(g) + CO(g)
Based on this value of Keq:
Go for this reaction is expected to be (greater,less) than zero.
Calculate the free energy change for the reaction of 2.43 moles of CH4(g) at standard conditions at 298K
greater
341
Calculate ΔrG° for the reaction below at 25.0 °C
2 Na(s) + 2
H2O() → 2 NaOH(aq) + H2(g)
given ΔrH° = –366.6 kJ/mol-rxn and
ΔrS° = –154.2 J/K×mol-rxn
–320.6 kJ/mol-rxn
The standard free energy change associated with the dissolution of ammonium nitrate in water is -13.0 kJ/mol at 356 K.
NH4NO3(s) NH4NO3(aq)
What is the equilibrium constant for the reaction?
81
The solubility of CaCrO4 is measured and found to be 4.04 g/L. Use this information to calculate a Ksp value for calcium chromate
6.7E-4
Calculate the solubility of copper(II) sulfide, CuS in units of grams per liter. Ksp(CuS) = 7.9E-37
8.5E-17