Chapter 4

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 1^o 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

1^st 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 + 6CO_2(g) + 6H₂O (l)_--->C₆H₁₂O_6(S)+ 6O₂(g)

C₆H₁₂O_6(s) + 6O2(g) ---> 6CO_2(g) + 6H₂O _(l)

We can ferment C₆H₁₂O6

yeast

C₆H₁₂O_{6(s)
--->}C₂H₅OH_(l)+ CO_2(g)

ethanol/ethyl alcohol

C₂H₅OH=3O₂--->2CO_{2
+}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