CHAPTER 4 - Energy-chem & Society

Energy - the ability to do work

Work - Force x Distance ---> W=Fd

Work = newton x meter = joule (kg x m2/sec2)

Heat - total internal E of substance

a) we’ll look @ molec. bonds

Temperature - measure of average kinetic E of molecules making up a substance

Potential Energy (PE) - E of position or arrangement

KINETIC ENERGY - (KE) -E of motion

Calorie - amt of E (heat) needed to release 1g H2O 1o C

4.184 J = 1 cal.

1 Cal = 1 kcal = 1,000 cal

1 ml H2O = 1 cm3 = 1g

 

Specific Heat of water = 1 cal/ g

Heat liberated = (change in degrees temp) x (mass) x (S.H.of H2O)

cal = (change in degrees C) x (g) x (1 cal/g)

or (oC)

Thermodynamics

1st law - law of conservation of E - E is neither created or destroyed - E in the universe is constant

Energy is transformed as it is transferred

1. CHEMICAL E

2. MECHANICAL E

3. RADIANT E

4. ELECTRICAL E

5. NUCLEAR E

Note : Heat is a by product. No real (?) Heat E

We could solve/calculate this

2800 KJ + 6CO2(g) + 6H2O (l) ---> C6H12O6(S) + 6O2(g)

C6H12O6(s) + 6O2(g) ---> 6CO2(g) + 6H2O (l)

 

We can ferment C6H12O6

yeast

C6H12O6(s) ---> C2H5OH(l) + CO2(g)

ethanol/ethyl alcohol

C2H5OH = 3O2 ---> 2CO2 + 3H2O + 1367kj

Bond E - amt. of E that must be absorbed too break a specific chemical bond

Endothermic - Process requiring the absorption of E

Exothermic - process accompanied by the release of heat E

Breaking - Endo Making - Exo

 

802.3kj/mol. CH4 x 1 mol CH4/16 g CH4 = 50.1 kj/g CH4

50.1 kj/g CH4 x 103 j/kj x 1 cal 4.184 j =11950 cal/g = 11.9 kcal/g

Since heat is evolved, decrease in energy in system reactants increase energy state than products

Products have lower PE

More E released forming products that required to break reactants

Daughter compounds stronger than parent compounds

Activation E - Energy to start the reaction

Useful fuels react @ rates neither to fast or to slow

Rotting wood - pg. 124

Size of particle

General Guidelines for compounds

Decrease O Increase E Combustion Act. E decrease

Fractioning tower p. 129

ISOMERS - Diff. compound w/ same molecular form

n- octane not so food - pre-ignition

catalyst

Iso - octane - resistant to pre-ignition

Kelvin = 0C+273

EFF = Th-Th/Th always less than 100%

Table 4.3 p. 137