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Question
Answer in brief.
How much heat is evolved when 12 g of CO reacts with NO2? The reaction is:
4CO(g) 2NO2(g) → 4CO2(g) + N2(g), ΔrH° = - 1200 kJ
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Solution
Given: ΔrH° = - 1200 kJ, Mass of CO = 12 g
To find: Heat evolved when 12g of CO reacts with NO2
Calculation:
According to the given reaction, 1200 kJ of heat is evolved when 4 moles of CO react with NO2. So heat evolved per mole is `(1200 "kJ")/(4 "mol")` = 300 kJ mol-1
Molar mass of CO = 12 + 16 = 28 g mol–1
Number of moles of CO = `"Mass of CO"/"Molar mass of CO" = (12 "g")/(28 "g mol"^-1)`= 0.4286 mol
So, heat evolved when 0.4286 moles of CO reacts
= 0.4286 mol × 300 kJ mol-1 = 128.58 kJ
The heat evolved when 12 g of CO reacts with NO2 is 128.58 kJ.
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