A. Directions: Solve the following problem using the thermochemical equation. Write your answer on your answer sheet. 1. Using the following thermochemical equation, calculate how much heat is associated with the decomposition of 4 mol of NH:C1. NH3g + HCl - NH,Cl AH- -176 kJ 2. How many grams of Na are needed to make -550.0 kJ? Na + 3Haig - 2NH AH - -92.6 kJ 3. Calculate the mass of ethane, CaHo which must be burned to produce 100 KJ of heat. 2C,Heg + 7019 → 4CO2 + 6H;O AH - -3120 KJ
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
![A. Directions: Solve the following problem using the thermochemical
equation. Write your answer on your answer sheet.
1. Using the following thermochemical equation, calculate how much heat
is associated with the decomposition of 4 mol of NH.CI.
NHJ + HCl - NH.Cl
AH- -176 kJ
2. How many grams of Na are needed to make -550.0 kJ?
Naw+ 3Ha + 2NHs
AH - -92.6 kJ
3. Calculate the mass of ethane, CaHo which must be burned to produce
100 KJ of heat.
2C,Heg + 70ag - 4CO2g + 6H,O
AH - -3120 KJ
B. Calculate the enthalpy change of the reaction using Hess's Law. Write your
answer on your answer sheet.
1. Calculate AH for the reaction CaHag + Ha -->C:Hoog, from the following
data.
C,Ha + 30a - 2COa + 2H,Om
C;Hoe + 7/20a - 200a + 3H,O
Hag + 1/20z - H20
AH - -1411. kJ/mole
AH - -1560. kJ/mole
AH - -285.8 kJ/mole
2. Calculate AH for the reaction 4NH3 + 50z0 - 4NO + 6H2O, from
the following data.
Na + Oz - 2NO
Naw + 3Ha - 2NH
2Hay + Oz + 2H20
AH - -180.5 kJ/mole
AH - -91.8 kJ/mole
AH - -483.6 kJ/mole
3. Calculate AH for the reaction 2Al(s) + 3Clg)
following data.
2Alm + 6HClaj - 2AIClang + 3Hag
HCh - HCl
Ha + Cla - 2HCI
AICls - AIClyjag)
- 2AICI, (s) from the
AH - -1049. kJ/mole
AH - -74.8 kJ/mole
AH - -1845, kJ/mole
AH - -323. kJ/mole
What I Can Do
1. The combustion of methane, CHa, releases 890.4 kJ/mol. That is, when
one mole of methane is burned, 890.4 kJ are given off to the
surroundings. This means that the products have 890.4 kJ less than
the reactants. Thus, AH for the reaction - -890.4 kJ. A negative symbol
for AH indicates an exothermic reaction.
CH:(g) + 20:(g) – CO:(g) + 2H;O)
A. Draw an energy diagram (profile) for the above equation, label all
parts.
B. How much energy is given off when 2.00 mol of CH, are burned?
C. How much energy is released when 22.4g of CH, are burned?
AH - -890.4 kJ
2. Calculate AH for the process
Hg-Clan + 2Hgn + Cla
from the following information:
Hga + Clag - HgCla
Hga + HgClaw+ Hg.Cla
AH - -224kJ
AH - -41.2KJ](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fdc572657-67ce-42a1-bcb4-bb407ae6e38e%2Fd54e0cf3-6aff-4787-b279-4efc50176542%2Fnupvlg9_processed.jpeg&w=3840&q=75)
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