Questions: How much heat is absorbed/released when burning 0.24 kg of acetylene with excess oxygen? Products are carbon dioxide and gaseous water. Heat (q) : a) -2.3 x 10^4 kJ b) 1.2 x 10^4 kJ c) -2.5 x 10^3 kJ d) 2.3 x 10^4 kJ e) -1.2 x 10^4 kJ

How much heat is absorbed/released when burning 0.24 kg of acetylene with excess oxygen? Products are carbon dioxide and gaseous water.
Heat (q) :
a) -2.3 x 10^4 kJ
b) 1.2 x 10^4 kJ
c) -2.5 x 10^3 kJ
d) 2.3 x 10^4 kJ
e) -1.2 x 10^4 kJ

Transcript text: How much heat is absorbed/released when burning 0.24 kg of acetylene with excess oxygen? Products are carbon dioxide and gaseous water. Heat (q) : a) $-2.3 \times 10^{4} \mathrm{~kJ}$ b) $1.2 \times 10^{4} \mathrm{~kJ}$ c) $-2.5 \times 10^{3} \mathrm{~kJ}$ d) $2.3 \times 10^{4} \mathrm{~kJ}$ e) $-1.2 \times 10^{4} \mathrm{~kJ}$

Solution

Solution Steps

Step 1: Determine the Chemical Reaction and Molar Mass

The combustion of acetylene ($\mathrm{C_2H_2}$) with oxygen ($\mathrm{O_2}$) produces carbon dioxide ($\mathrm{CO_2}$) and water ($\mathrm{H_2O}$):

\[ 2 \mathrm{C_2H_2} + 5 \mathrm{O_2} \rightarrow 4 \mathrm{CO_2} + 2 \mathrm{H_2O} \]

The molar mass of acetylene ($\mathrm{C_2H_2}$) is calculated as follows:

\[ \text{Molar mass of } \mathrm{C_2H_2} = 2 \times 12.01 \, \mathrm{g/mol} + 2 \times 1.008 \, \mathrm{g/mol} = 26.036 \, \mathrm{g/mol} \]

Step 2: Calculate the Moles of Acetylene

Given the mass of acetylene is 0.24 kg (or 240 g), we can calculate the number of moles:

\[ \text{Moles of } \mathrm{C_2H_2} = \frac{240 \, \mathrm{g}}{26.036 \, \mathrm{g/mol}} = 9.217 \, \mathrm{mol} \]

Step 3: Determine the Heat of Combustion

The heat of combustion for acetylene is typically given as $-1300 \, \mathrm{kJ/mol}$. This value represents the heat released when one mole of acetylene is burned.

Step 4: Calculate the Total Heat Released

Using the moles of acetylene and the heat of combustion, we can calculate the total heat released:

\[ q = 9.217 \, \mathrm{mol} \times (-1300 \, \mathrm{kJ/mol}) = -11982.1 \, \mathrm{kJ} \]