If the acetylene were burned to form water and carbon dioxide, how many kilojoules of energy would be produced from the complete reaction of 20 of calcium carbide?
CaC2(s)+2H2O(l) --> C2H2(g)+Ca(OH)2(s)
To calculate the amount of energy produced from the complete reaction of 20 moles of calcium carbide, we need to determine the quantity of acetylene (C2H2) produced and then use the enthalpy of formation values to calculate the energy released.
Step 1: Calculate the moles of acetylene produced.
From the balanced chemical equation, we can see that 1 mole of calcium carbide (CaC2) produces 1 mole of acetylene (C2H2). Therefore, since we have 20 moles of calcium carbide, we will also have 20 moles of acetylene.
Step 2: Determine the enthalpy of formation.
The enthalpy of formation (ΔHf) is the energy change that occurs when one mole of a compound forms from its elemental components in their standard states. We need to use the ΔHf values of calcium carbide (CaC2), acetylene (C2H2), water (H2O), and carbon dioxide (CO2) to calculate the energy released.
The ΔHf values are as follows:
ΔHf(CaC2) = -59.4 kJ/mol
ΔHf(C2H2) = +227.4 kJ/mol
ΔHf(H2O) = -285.8 kJ/mol
ΔHf(CO2) = -393.5 kJ/mol
Step 3: Calculate the energy released.
Since the reaction produces 1 mole of acetylene (C2H2) for every mole of calcium carbide (CaC2), we can calculate the total energy released using the following equation:
Energy Released = ΔHf(CaC2) + 2 * ΔHf(H2O) - ΔHf(C2H2) - ΔHf(Ca(OH)2)
By substituting the values:
Energy Released = (-59.4 kJ/mol) + 2 * (-285.8 kJ/mol) - (227.4 kJ/mol) - 0 kJ/mol
Energy Released = -59.4 kJ/mol - 571.6 kJ/mol - 227.4 kJ/mol
Energy Released = -858.4 kJ/mol.
Finally, we multiply the energy released per mole by the number of moles:
Energy Produced = Energy Released * Number of Moles
Energy Produced = -858.4 kJ/mol * 20 mol
Energy Produced = -17,168 kJ
Therefore, the complete reaction of 20 moles of calcium carbide would produce approximately -17,168 kilojoules (kJ) of energy. Note that the negative sign indicates the energy is released or exothermic.