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)
20 what? grams?
dHrxn = (n*dHf products) - (n*dHf reactants)
q for 20g = dHrxn x (20/molar mass CaC2)
To calculate the amount of energy produced from the complete reaction of 20 grams of calcium carbide, we need to use the balanced equation:
CaC2(s) + 2H2O(l) → C2H2(g) + Ca(OH)2(s)
From the equation, we can see that 1 mole of calcium carbide (CaC2) reacts to produce 1 mole of acetylene (C2H2). To determine the number of moles of calcium carbide, we first need to calculate its molar mass.
The molar mass of CaC2 is calculated by adding up the atomic masses of each element present in it. Calcium (Ca) has an atomic mass of 40.08 g/mol, and carbon (C) has an atomic mass of 12.01 g/mol. Since there are two carbon atoms in calcium carbide, we multiply the atomic mass of carbon by 2. Therefore:
Molar mass of CaC2 = (40.08 g/mol) + (12.01 g/mol × 2) = 64.10 g/mol
Next, we calculate the number of moles of calcium carbide by dividing the mass given (20g) by its molar mass:
Number of moles of CaC2 = 20g / 64.10 g/mol ≈ 0.312 moles
From the balanced equation, it can be observed that 1 mole of CaC2 reacts to form 1 mole of C2H2 (acetylene). Therefore, 0.312 moles of CaC2 will produce the same number of moles of C2H2.
To calculate the energy produced, we need to know the heat of combustion value for acetylene. The heat of combustion for acetylene (C2H2) is approximately -1300 kJ/mol.
Finally, we can calculate the energy produced by multiplying the number of moles of acetylene with the heat of combustion value:
Energy produced = 0.312 moles × -1300 kJ/mol
Therefore, about -406.3 kJ (rounded to the nearest tenth) would be produced from the complete combustion of 20 grams of calcium carbide.