Consider the combustion of propane:
C3H8(g)+5O2(g) yields 3CO2(g) + 4H2O(l)
delta H= -2221 kJ
Assume that all of the heat comes from the combustion of propane. Calculate delta H in which 5.00g of propane is burned in excess oxygen at constant pressure.
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To calculate the change in enthalpy (ΔH) when 5.00g of propane is burned in excess oxygen at constant pressure, we can use stoichiometry and the given enthalpy change of combustion (ΔH = -2221 kJ).
1. Determine the molar mass of propane (C3H8):
- The molar mass of carbon (C) is 12.01 g/mol, and there are 3 carbon atoms in propane.
- The molar mass of hydrogen (H) is 1.01 g/mol, and there are 8 hydrogen atoms in propane.
- Therefore, the molar mass of propane (C3H8) is (3 * 12.01 g/mol) + (8 * 1.01 g/mol) = 44.11 g/mol.
2. Convert the given mass of propane to moles:
- The molar mass of propane is 44.11 g/mol.
- Therefore, the number of moles of propane is 5.00 g / 44.11 g/mol = 0.1132 mol.
3. Use the stoichiometric coefficients to determine the molar ratio between propane and CO2:
- The stoichiometric coefficient of propane in the balanced equation is 1.
- The stoichiometric coefficient of CO2 in the balanced equation is 3.
- Therefore, for 1 mole of propane, 3 moles of CO2 are formed.
4. Calculate the moles of CO2 produced:
- Multiply the number of moles of propane by the ratio from step 3: 0.1132 mol * (3 mol CO2 / 1 mol propane) = 0.3396 mol CO2.
5. Calculate the amount of heat released based on the given enthalpy change:
- ΔH = -2221 kJ/mol (given)
- Multiply ΔH by the moles of CO2 produced: -2221 kJ/mol * 0.3396 mol CO2 = -754.1536 kJ.
Therefore, the change in enthalpy when 5.00g of propane is burned in excess oxygen at constant pressure is approximately -754.15 kJ.
To calculate the change in enthalpy (ΔH) for the combustion of propane, you need to use the given information about the balanced chemical equation and the enthalpy change value. Here's how you can solve it step by step:
Step 1: Calculate the moles of propane (C3H8) used.
To do this, use the molar mass of propane, which is 44.1 g/mol:
Moles of C3H8 = Mass of C3H8 / Molar mass of C3H8
Moles of C3H8 = 5.00g / 44.1 g/mol
Step 2: Determine the molar ratio between propane and CO2.
Referencing the balanced chemical equation:
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l)
From the equation, you can see that 1 mole of propane produces 3 moles of CO2.
Step 3: Calculate the moles of CO2 produced.
Moles of CO2 = Moles of C3H8 × (3 moles of CO2 / 1 mole of C3H8)
Step 4: Calculate the heat released.
Next, you'll use the information given: ΔH = -2221 kJ (the enthalpy change) and the moles of CO2 calculated in step 3.
Heat released = Moles of CO2 × ΔH
Step 5: Convert kJ to J, as we're dealing with grams in the question.
Heat released (J) = Heat released (kJ) × 1000
Once you've followed these steps, you should arrive at the final value for the change in enthalpy (ΔH) in Joules.