Entropy
If a reaction is spontaneous what is the likely sign of deltaS?
(+)
Is a reaction most likely spontaneous or nonspontaneous when deltaH is (-)
The rxn is most likely spontaneous, but it will depend on the entropy
What is the sign of deltaG if a reaction is spontaneous
deltaG= (-)
What is the first law of thermo?
Energy can't be created or destroyed
True or False:
Molecules need to be in a specific orientation for a reaction to occur.
True
If a solid is turned into a liquid, is entropy increasing or decreasing?
Entropy is increasing
If the system is absorbing energy, is the deltaH positive or negative?
Enthalpy would be (+), endothermic
An amount of usable energy (energy that can do work, so NOT heat energy) in a system is...
Gibbs Free Energy
What is the second law of thermo?
Entropy of the universe is always increasing
N2 (g) + 3H2 (g) → 2NH3 (g)
What is the rate equation for this reaction?
Rate = -𝜟[N2]/𝜟t = -1/3(𝜟[H2]/𝜟t) = 1/2(𝜟[NH3]/𝜟t)
If an aqueous solution suddenly creates a precipitate by the addition of a metal, is the entropy of the system increasing or decreasing?
Entropy will decrease
What is the equation for determining change in enthalpy?
deltaH = (Products) - (Reactants)
MnO2(s)⟶ Mn(s) + O2(g) At 25°C, ΔH= -520.03 kJ/mol, ΔS=53.05 J/K/mol
At 25°C, is this reaction spontaneous?
YES!
What happens to molecules in a solution when the temperature increases?
The velocity of the molecules increase
N2 + 3H2 → 2NH3
What is the rate of formation of ammonia in comparison to the rate of loss of hydrogen?
Δmol NH3 = 2Δmol NH3/-3Δmol H2, so -⅔.
2NO2 (g) ⇌ N2O4 (g)
The △S◌ for N2O4 is 304.29 J/(mol*K) and for NO2 is 240.06 J/(mol*K). What sign does the △Ssurr have to be in order for this reaction to be nonspontaneous?
△Ssurr= (+)
NaOH (aq) + HCl (aq) → H2O (l) + NaCl (aq)
The △HNaOH=-470.1 kJ/mol , △HHCl=-167.2 kJ/mol , △HH2O=-285.8 kJ/mol , △HNaCl=-407.25 kJ/mol Is this reaction endothermic or exothermic?
Exothermic
P4 (g) + 6Cl2 (g) → 4PCl3
△G◌P4= 24.4 kJ/mol, △G◌Cl2= 0 kJ/mol, △G◌PCl3= -269.6 kJ/mol Calculate the standard free energy change for the reaction.
-1102.8 kJ/mol
What does it mean when the enthalpy change for a reaction is negative?
The reaction is exothermic
2H2O2→ 2H2O+O2
You have a reaction where hydrogen peroxide is decomposing at a constant rate of 88.88 mM/s. What rate is the oxygen gas forming at?
88.88 *-½ = 44.44 mM/s
If 3 molecules are clumped on the right side of a container and then allowed to dispurse, you observe that there are now 2 molecules on the left and one on the right. If this is a nonspontaneous reaction, what is the sign of △Ssurr ?
△Ssurr= (-)
Pb(s) + Cl2(g) → PbCl2(s) △H= -359.4 kJ
Ni(s) +Cl2(g) → NiCl2(s) △H= -305.3 kJ Calculate the enthalpy change for the reaction below:
PbCl2(s) + Ni(s) → NiCl2(s) + Pb(s)
54.1 kJ
Calculate the △G of a reaction if:
△S = -198.75 J/(mol*K), △H = -92.22 kJ, T = 500◌C
61.41 kJ/mol
Enthalpy change is...
the amount of energy as heat that is lost or gained by a system
Time= 0 Conc=1.00 x 10-2 Time=1600s Conc=5.04 x 10-3
What is the average rate of change for the total time, and between 0 and 1600 s?
(5.04x10-3- 10-2) / (1600 - 0)= -3.10x10-6 M/s