Spontawhat?
Endo Exo
Hess Hess Baby
Bond Energy
Stoich is Fun
100
What is the sign of ΔG when a reaction is spontaneous?
negative
100
Is the following process endothermic or exothermic?
Endothermic
100
Calculate the value of ∆H° for the reaction
C2H5OH (l) → CH3OCH3 (l).
from the following enthalpy change:
C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H2O (g) ∆H° = -1234.7 kJ
CH3OCH3 (l) + 3O2 (g) → 2CO2 (g) + 3H2O (g) ∆H° = -1328.3 kJ
1)keep -1234.7
2)flip +1328.3
=93.6 kJ
100
This requires energy.
Breaking bonds
100
How do you convert grams to moles?
divide by molar mass!
200
This type of system will never be spontaneous.
positive enthalpy and negative entropy
200
Is the following process endothermic or exothermic?
Frying an egg
Endothermic
200
Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
N2H4 (l) + H2(g) → 2 NH3(g)
Given:
N2H4(l) + CH4O(l) → CH2O(g) + N2(g) + 3 H2 (g) ΔH = -37 kJ
N2(g) + 3 H2(g) → 2 NH3(g) ΔH = -46 kJ
CH4O(l) → CH2O(g) + H2(g) ΔH = -65 kJ
1) keep -37 kJ
2) keep -46 kJ
3) flip +65 kJ
= -18 kJ
200
What type and how many bonds are in the reactants of the following reaction:
CO + 2H2 → CH3OH
(C≡O) and 2(H-H)
200
How much heat will be released when 4.72 g of carbon reacts with excess O2 according to the following equation?
C + O2 →CO2 ∆H = -393.5 kJ
-155 kJ
300
Describe a process that results in an increase in the entropy of the system?
examples: dissolution of solid KCl in water, mixing of two gases into one container, melting ice to form water E) boiling water to form steam
300
In the diagram below, how much energy is released when bonds form?
-80 kJ
300
Determine the ΔH value for the reaction below:
Fe2O3(s) + CO(g) → 2FeO(s) + CO2(g)
The following two reactions are known:
Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g) ΔH = −23.44 kJ
FeO(s) + CO(g) → Fe(s) + CO2(g) ΔH = −10.94 kJ
1) Keep = -23.44 kJ
2) Flip and multiply by 2 = +21.88 kJ
=-1.56 kJ
300
Calculate the energy needed to break the bonds in the following reaction (using the table of bond energies in the Bond Energy POGIL):
=+1392 kJ/mol
(C-H) + 3(C-Cl)= 411 kJ/mol + 3(327 kJ/mol)
300
How much heat will be released when 6.44 g of sulfur reacts with excess O2 according to the following equation?
2 S + 3 O2 → 2 SO3 ∆H = -791.4 kJ
-79.5 kJ
400
Consider the reaction: C2H6 → C2H4 + H2
The ΔH is 137 kJ and the ΔS is 120 J/K. Under what conditions will it be spontaneous?
high temps!
400
In the diagram below, how much energy is required to break the bonds?
200 kJ
400
Calculate the enthalpy for this reaction:
2C(s) + H2(g) → C2H2(g)
Given the following thermochemical equations:
C2H2(g) + 5⁄2 O2(g) → 2CO2(g) + H2O(ℓ) ΔH = −1299.5 kJ
C(s) + O2(g) → CO2(g) ΔH = −393.5 kJ
H2(g) + 1⁄2 O2(g) → H2O(ℓ) ΔH = −285.8 kJ
1) Flip = +1299.5 kJ
2) Multiply by 2 = -787 kJ
3) Keep = -285.8 kJ
=+226.7 kJ
400
Calculate the energy released when bonds are formed in the following reaction (using the table of bond energies in the Bond Energy POGIL):
= -3094 kJ/mol
-[4(C-H) + 2(C-F) +(C-C)]= -[4(411 kJ/mol) + 2(552 kJ/mol) +346]
400
How much heat will be transferred when 5.81 g of hydrogen reacts with excess graphite according to the following reaction? Is this reaction endothermic or exothermic?
6 C (graphite) + 3 H2 → C6H6 ∆H = 49.03 kJ
+47.1 kJ absorbed
endothermic
500
Consider the reaction: C2H6 → C2H4 + H2
The ΔH is 137 kJ and the ΔS is 120 J/K. At what temperature will the sign of ΔG change?
1140 K
500
In the diagram below, is more energy required to break bonds or released when bonds are formed?
More energy is required to break the bonds.
500
Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
PCl5(g) → PCl3(g) + Cl2(g)
Given:
P4(s) + 6 Cl2(g) → 4 PCl3(g) ΔH = - 2439 kJ
4 PCl5(g) → P4(s) + 10 Cl2(g) ΔH = + 3438 kJ
1) Divide by 4= -609.75 kJ
2) Divide by 4= +859.5 kJ
=+249.75 kJ
500
Calculate ΔH for the following reaction (using the table of bond energies in the Bond Energy POGIL):
=0 kJ
6(C-H) + 2(C-O) + 2(O-H) - [6(C-H) + 2(C-O) + 2(O-H)]
500
9. How much heat will be transferred when 14.9 g of ammonia (NH3) reacts with excess O2 according to the following equation?
Is this reaction endothermic or exothermic?
4 NH3 + O2 → 4 NO + 6 H2O ∆H = -1170 kJ
-256 kJ
exothermic