1. The thermochemical equation for the combustion of ethanol is as follows: C 2
ID: 703850 • Letter: 1
Question
1. The thermochemical equation for the combustion of ethanol is as follows:
C2H5OH(l) + 3 O2(g) ? 2 CO2(g) + 3 H2O(g) ?H = ?1367 kJ
How many kilojoules of heat would be produced by the complete combustion of 75.0 mL of pure ethanol? The density of ethanol is 0.789 g/mL.
2. The reduction of iron(III) oxide to iron metal is an endothermic process:
Fe2O3(s) + 2 CO(g) ? 2 Fe(s) + 3 CO2(g) ?H = +26.3 kJ
How many kilojoules of energy are required to produce 1.00 kilogram of iron metal?
3. Consider the following balanced reaction. How many grams of water are required to form 1.20 moles of HNO3? Assume that there is excess NO2 present.
3 NO2(g) + H2O(l) ? 2 HNO3(aq) + NO(g)
Explanation / Answer
Ans 1
The balanced reaction
C2H5OH(l) + 3 O2(g) = 2 CO2(g) + 3 H2O(g)
H = - 1367 kJ
Mass of ethanol = volume x density
= 75 mL x 0.789 g/mL
= 59.175 g
Moles of ethanol = mass/molecular weight
= 59.175 g / 46.07 g/mol
= 1.284 mol
1 mol ethanol Produces heat = - 1367 kJ
1.284 mol ethanol produces heat = - 1367 x 1.284
= - 1755.85 kJ
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