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Acetylene gas (ethyne; HC?CH) burns in an oxyacetylene
Chapter 9, Problem 57P(choose chapter or problem)
Acetylene gas (ethyne; HC≡CH) burns in an oxyacetylene torch to produce carbon dioxide and water vapor. The heat of reaction for the combustion of acetylene is 1259 kJ/mol. (a) Calculate the C≡C bond energy, and compare your value with that in Table 9.2, p. 353. (b) When 500.0 g of acetylene burns, how many kilojoules of heat are given off? (c) How many grams of CO2 form? (d) How many liters of O2 at 298 K and 18.0 atm are consumed?
Questions & Answers
QUESTION: Problem 57P
Acetylene gas (ethyne; HC≡CH) burns in an oxyacetylene torch to produce carbon dioxide and water vapor. The heat of reaction for the combustion of acetylene is 1259 kJ/mol. (a) Calculate the C≡C bond energy, and compare your value with that in Table 9.2, p. 353. (b) When 500.0 g of acetylene burns, how many kilojoules of heat are given off? (c) How many grams of CO2 form? (d) How many liters of O2 at 298 K and 18.0 atm are consumed?
ANSWER:
Solution 57P
Step 1
(a) Here we have to calculate the C≡C bond energy, and have to compare our value with that in Table 9.2, p. 353.
In this question it has been given that, acetylene gas (ethyne; HC≡CH) burns in an oxyacetylene torch to produce carbon dioxide and water vapor. The heat of reaction for the combustion of acetylene is 1259 kJ/mol.
The combustion reaction for acetylene gas is given below,
C2H2 + 5/2 O2 → 2CO2 + H2O = -1259 kJ/mol
H-CC-H + 5/2 O=O → 2 O=C=O + H-O-H
The heat of reaction can be calculated as, =
+
= [2BEC-H + BEC
C + 5/2 BEO=O] + [4(-BEC=O) + 2(-BEO-H)]
-1259 kJ = [2(413) + BECC + 5/2 (498)] + [4(-799) +2 (-467)]
-1259 kJ = [826 + + BECC + 1245] + [-4130] kJ
-1259 kJ = -2059 + BECC kJ
BECC = 800.0 kJ/mol
Thus the bond energy of CC is found to be 800.0 kJ/mol whereas in table 9.2, the value is listed as 839 kJ/mol.