When 1 mole of ethylene (C2H4) is burned at constant pressure, 1410 kJ of energy is released as heat. Calculate dH for a process in which 10.0 g of ethylene is burned at constant pressure.
I showed you how to do this yesterday. Why are you posting again?
To calculate ΔH (change in enthalpy) for the given process, we need to use the molar mass of ethylene and convert the given mass into moles. Here are the step-by-step calculations:
1. Find the molar mass of C2H4:
- Carbon (C) has a molar mass of approximately 12.01 g/mol.
- Hydrogen (H) has a molar mass of approximately 1.01 g/mol.
- Multiply the molar mass of carbon by 2 and that of hydrogen by 4, then add both results to get the molar mass of ethylene (C2H4):
molar mass (C2H4) = (2 × 12.01 g/mol) + (4 × 1.01 g/mol) = 28.05 g/mol
2. Calculate the number of moles of ethylene in 10.0 g:
- Divide the given mass by the molar mass of ethylene:
moles of C2H4 = mass / molar mass
= 10.0 g / 28.05 g/mol
≈ 0.356 mol
3. Calculate the energy released for 1 mole of ethylene:
- Given that when 1 mole of ethylene is burned, 1410 kJ of energy is released as heat.
- Therefore, the energy released per mole is 1410 kJ/mol.
4. Calculate the change in enthalpy for the given process:
- Multiply the energy released per mole by the number of moles of ethylene burned:
ΔH = energy released per mole × moles of C2H4
= 1410 kJ/mol × 0.356 mol
≈ 501.96 kJ
Therefore, ΔH for the process in which 10.0 g of ethylene is burned at constant pressure is approximately 501.96 kJ.
To calculate dH for the process, we need to use the concept of molar heat of combustion. The molar heat of combustion (dH) is the amount of heat released or absorbed when one mole of a substance is burned completely under constant pressure.
Given:
- The molar heat of combustion (dH) for ethylene is 1410 kJ/mol.
We are required to calculate dH for a process in which 10.0 g of ethylene is burned. Let's break down the steps to solve this problem:
Step 1: Calculate the number of moles of ethylene burned.
To determine the moles of ethylene, we need to use the molar mass of ethylene (C2H4), which is calculated by adding the atomic masses of its constituent elements.
C2H4: 2(12.01 g/mol) + 4(1.01 g/mol) = 28.05 g/mol
Number of moles = Mass (g) / Molar Mass (g/mol)
Number of moles = 10.0 g / 28.05 g/mol
Step 2: Calculate dH for the given mass of ethylene.
dH = Number of moles of ethylene × dH per mole
Substituting the values:
dH = (10.0 g / 28.05 g/mol) × 1410 kJ/mol
Step 3: Calculate the answer.
Perform the calculations using a calculator:
dH = (10.0 / 28.05) × 1410
The final answer will be the value of dH obtained from the calculation.
Please note that the molar heat of combustion (dH) is usually expressed with a negative sign since it is an exothermic process (heat is released). So the final answer should have a negative sign to indicate the heat released.
one mole of ethylene is about 28 grams
10/28=dH/1410kj