Concepts 1
Concepts 2
Hess's Law
Bond Energy
Stoichiometry
100
Is the following process endothermic or exothermic?
Exothermic
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
What is the formula for calculating enthalpy using bond energy?
ΔHrxn=Σbonds broken - Σbonds formed
100
How do you convert grams to moles?
Stoichiometry using molar mass!
200
What is the difference between heat and temperature? Which do we feel?
Temperature is the measure of the kinetic energy of particles. Heat is the flow of thermal energy between objects. We feel heat.
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
Is the following process endothermic or exothermic?
Rain forming from water vapor in the clouds
Exothermic
300
A 60℃ piece of iron is placed in boiling water, which direction will the heat flow, and what temperature will the metal and water be when heat stops flowing?
Heat will flow from high to low temperatures, so from the water to the iron. The temperature will be 80℃ when heat stops flowing.
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
In the diagram below, how much energy is released when bonds form?
-80 kJ
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):
= -2748 kJ/mol
-[4(C-H) + 2(C-F)]= -[4(411 kJ/mol) + 2(552 kJ/mol)]
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
In the diagram below, what is the change in enthalpy?
-20 kJ
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