Chem31 Chapt. 9, pt. I: Energy, Enthalpy & Ideal Gases

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Chem31 Chapt. 9, pt. I: Energy, Enthalpy & Ideal Gases by Mind Map: Chem31 Chapt. 9, pt. I: Energy, Enthalpy & Ideal Gases

1. Energy in Daily Life

1.1. Chemical Sources

1.1.1. Fossil fuel

1.1.2. Biomass

1.1.3. Food

1.1.4. Mineral deposits

1.1.5. Nuclear fission & fusion

1.2. Non-chemical Sources

1.2.1. Light

1.2.2. Gravitation

1.2.3. Motion (waves, wind)

2. Definitions & Laws of Energy

2.1. Energy: capacity to do work or produce heat

2.2. Law of Conservation of Energy

2.2.1. Can be converted from one form to another

2.2.2. Can be neither created or destroyed

3. Classifications of Energy

3.1. Potential Energy

3.2. Kinetic Energy E1

3.3. Interconversion Between Kinetic & Potential Energy E2

4. Heat & Work

4.1. Difference between heat & temperature

4.1.1. Temperature: property reflecting the random motions of particles within a substance

4.1.2. Heat: transfer of energy between objects: not conserved, not a substance

4.2. Work: Force acting over a distance

4.3. Two ways to transfer nrg: heat & work

4.4. Proportion of heat & work depends on process

5. Chemical Energy

5.1. Combustion of methane: energy as a product E3

5.2. Universe is divided into two parts

5.2.1. System: part of system on which we want to focus attention (e.g. reactants & products)

5.2.2. Surroundings: everything else

5.3. Heat and chemical reactions

5.3.1. Exothermic reaction: evolves heat: nrg flows out of system into surroundings (e.g. combustion of methane) F1

5.3.2. Endothermic reaction: absorbs heat: energy flows from surroundings into the system (e.g. formation nitric oxide from nitrogen & oxygen) E4, F2

5.4. Relative energy of reactants & products

5.4.1. Exothermic reaction: Bond in products stronger than reactants: energy is a product

5.4.2. Endothermic reaction: Bonds of products weaker than reactants: energy is a reactant

6. Thermodynamics: study of energy and its interconversions

6.1. 1st Law of Thermo: The energy of the universe is constant

6.1.1. Conservation of energy

6.1.2. The energy lost by a system is equal to the energy gained by the surroundings

6.2. The internal energy (E) of a system is the sum of the kinetic and potential energy of all of its particles

6.2.1. When a change in the internal energy of a system occurs there is a flow of heat and/or work done E5

6.3. SIGN CONVENTIONS: from system's point of view F3

6.3.1. q positive when heat flows into the system from the surroundings (endothermic)

6.3.2. q negative when heat flows out of the system to the surroundings (exothermic)

6.3.3. w positive when work is done on the system by the surroundings nrg from surroundings into system

6.3.4. w negative when work is done by the system on the surroundings (nrg from system into surroundings

6.4. Pressure-volume work (PV) of a gas in a cylinder F4

6.4.1. Expansion: work done by a gas on the surroundings (w<0)

6.4.2. Compression: work done on a gas by the surroundings (w>0)

6.4.3. Pressure: Force/Area (external pressure)

6.4.4. Work= Force x Distance E6

6.4.5. w=-PΔV

7. Enthalpy

7.1. Definition: H= E +PV

7.1.1. E: internal energy of system

7.1.2. P: pressure of system

7.1.3. V: Volume of system

7.1.4. All state functions, so H is also a s.f.

7.2. Process at constant pressure where only PV work allowed (w=-PΔV)

7.2.1. ΔE=q+w

7.2.2. ΔE=q-PΔV

7.2.3. q=ΔE+PΔV

7.2.4. ΔH=ΔE+Δ(PV)

7.2.5. At constant P, Δ(PV)=PΔV, so ΔH=ΔE+PΔV

7.2.6. ΔH=q: at constant pressure a process with only PV work, change in enthalpy is equal to the flow of energy as heat

7.3. For a chemical reaction, the enthalpy change, is ΔH=Hproducts-Hreactants

8. Thermodynamics of Ideal Gases T2

8.1. Ideal Gas Law: PV=nRT

8.2. Kinetic energy of an ideal gas: KE=3/2RT

8.2.1. The only way to change the kinetic energy of an ideal gas is to change its temperature

8.2.2. Heat required to raise the temperature of an ideal gas = 3/2RΔT

8.2.3. molar heat capacity: nrg required to raise the temperature of a substance by 1 K

8.3. Heating an ideal gas at constant volume

8.3.1. ΔV=0, therefore no PV work

8.3.2. Cv=3/2R

8.4. Heating an ideal gas at constant pressure

8.4.1. Volume changes, work is done

8.4.2. Energy required="heat"=energy to change translational energy+energy to do work

8.4.3. work=PΔV=nRΔT=RT per mole=R per mole per 1 K

8.4.4. heat = Cp = 3/2R + R= 5/2 R or Cv+R

8.5. Heating a polyatomic gas T1

8.5.1. Cv is higher than for monatomic gas because of rotational and vibrational motion

8.5.2. Cp still= Cv+ R

9. State Functions

9.1. Property that depends on the present state of system, not on its past or future

9.2. Change in a state function in going from one state to another is independent of the pathway it takes

9.3. Energy is a state function, heat and work are not

10. de