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Give the 3 Importance and 3 applications of Enthalphy
Solve Me!
1. Calculate the heat of hydrogenation of ethane, C2H4 given the following thermochemical equations:
2 C (graphite) + 3 H2 (g) --> C2H6 (g) ∆H=-84.5 kJ/mol
2 C (graphite) + 2 H2 (g) --> C2H4 (g) ∆H= 52.3 kJ/mol
2. Calculate the ∆H for the reaaction:
CS2 (I) + 2 O2 (g) CO2 (g) + 2 SO2 (g)
given:
∆HrCO2 (g)= -393.5 kJ/mol;
∆HrSO2= -296.8 kJ,/mol;
∆HrCS2 (I) = 87.9 kJ/mol
Calculate Me
Given the thermochemical equation
2SO2(g) + O2 SO3(g) ---> ∆H= -198.2 kJ/mol
Calculate the heat evolved when 87.9 g of SO2 (molar mass 64.07 g/mol) is convertedto SO3.
Fill in the blanks with the comcepts related to the Enthalpy of Chemical Reactions to complete the following statements.
1. The term enthalpy is from the Greek word enthalpein meaning ________
2. The symbol for the change in enthalpy is ________ also referred to as heat of the reaction.
3. A positive sign for the change in enthalpy indicates that the process is ___________.
4. A negative sign for the change in enthalpy indicates that process is __________
5. Change un enthalpy depends on the _________ and not on the path.
Write the thermochemical equation for the following reactions that occur at constant pressure.
Example :
Decomposition of mercuric oxide HgO to mercury Hg and Oxygen O2 gas, requires 87.1 Kj of heat
HgO(s) --> Hg(/) + O2(g) ∆H= + 87.1 kJ(needs to absorb energy)
1. Combustion of hexane,C6H12 to carbon dioxide gas and water, releases 3923.9 kJ of heat.
2. Reaction between solid phosphorous, P4 and oxygen gas, produces P3O5 and 1640.1kJ of heat.
3. One mole ammonium nitrate (NH4NO) dissolves in water to produce aqueous ammonium ions and nitrate ions accompanied by the absorption of 28.1kJ of heat.
4. Formation of carbon dioxide gas from carbon (graphite) and oxygen yields 393.5 kJ of heat.
Determine whether the following processes are endothermic or exothermic given the equation and value for the change in ethalpy.
1. Conversion of methyl alcohol to carbon monoxide and hydrogen
CH2OH --> CO2 + 2H2 ∆H= +90.7kj
2. Formation of hydrofluoric acid from hydrogen and flourine
H2 + F2 --> 2HF ∆H= -557kj
3.Combustion of acetone
C3H6O + 4O2 --> 3CO2 + 3H2O ∆H= -1790kJ
4. Formation of methane gas from graphite and hydrogen
C + 2H2 --> CH4 ∆H= -74.7kJ
5. Evaporation of water
2 H2O(/) --> 2 H2O(g) ∆H= +88 kJ
Identify whether the following are exothermic or endothermic processes.
1. Melting Ice
2. Freezing of water
3. Evaporation of a bathroom deodorizer
4. Burning a piece of wood
5. Photosynthesis
EXPLAIN!
Juliet was studying about thermodynamics. She was doing well in understanding the lesson except for one concept. She was confused between the two terms, heat and temperature. Are heat and temperature the same? Explain the difference between the two terms?
Solve Me!
1. Manuel has a container that contains a sample of nitrogen gas and a tightly fitting movable piston that does not allow any of the gas to escape. During a thermodynamics process, 200 Joules of heat enter the gas, and the gas does 300 Joules of work in the process. What was the change in internal energy of the gas during the process described above?
2. The work done when a gas is compressed in a cylinder is 462 J. During this process, there is a heat transfer of 128 J from the gas to the surroundings. Calculate the energy change for this process.
For a reaction with the rate law of
Rate = k[A][B]2
Which of the following will not change k?
a. Adding an inhibitor
b. Adding a catalyst
c. Raising the temperature of the mixture
d. Increasing [A]
