1. What mass of carbon is required to produce 100kj of heat, when burned in air? Enthalpy change = -392kj.
2. What mass of methanol is required to produce 1000kj of heat, when burned in air?
C + O2 ==> CO2
392 kJ/mol x ? mol = 100 kJ
Then ?mol = grams/molar mass. You know mol and you know molar mass; solve for grams.
Got it - thank you.
To determine the mass of carbon or methanol required to produce a certain amount of heat when burned in air, we can use the concept of enthalpy change, which is the heat released or absorbed during a chemical reaction.
1. Mass of Carbon:
The given enthalpy change for the combustion of carbon is -392 kJ. This value represents the heat released when one mole of carbon is burned. To calculate the mass of carbon required to produce 100 kJ of heat, you can follow these steps:
Step 1: Find the number of moles of carbon required.
- We know that the enthalpy change for one mole of carbon is -392 kJ.
- Using the equation: Energy (in kJ) = Enthalpy change (in kJ/mol) x Moles, we can rearrange the equation to solve for moles:
100 kJ = -392 kJ/mol * Moles
Moles = 100 kJ / -392 kJ/mol
Moles ≈ -0.255 mol
Step 2: Calculate the molar mass of carbon (C).
- The atomic mass of carbon is approximately 12.01 g/mol.
Step 3: Find the mass of carbon required.
- Multiply the moles calculated in Step 1 by the molar mass of carbon:
Mass = Moles * Molar mass
Mass = -0.255 mol * 12.01 g/mol
Mass ≈ -3.06 g
Therefore, approximately 3.06 grams of carbon is required to produce 100 kJ of heat when burned in air.
2. Mass of Methanol:
Using a similar approach, you can calculate the mass of methanol required to produce 1000 kJ of heat when burned in air.
Step 1: Find the number of moles of methanol required.
- We know that the enthalpy change for the combustion of methanol is given.
- Apply the same equation: Energy (in kJ) = Enthalpy change (in kJ/mol) x Moles, and rearrange to solve for moles:
1000 kJ = Enthalpy change (in kJ/mol) * Moles
Moles = 1000 kJ / Enthalpy change (in kJ/mol)
Step 2: Calculate the molar mass of methanol (CH3OH).
- The molar mass of carbon (C) is approximately 12.01 g/mol.
- The molar mass of hydrogen (H) is approximately 1.01 g/mol.
- The molar mass of oxygen (O) is approximately 16.00 g/mol.
- Calculate the total molar mass of methanol: Molar mass = (12.01 g/mol) + (3 * 1.01 g/mol) + (16.00 g/mol).
Step 3: Find the mass of methanol required.
- Multiply the moles calculated in Step 1 by the molar mass of methanol:
Mass = Moles * Molar mass
By following these steps, you can calculate the mass of methanol required to produce 1000 kJ of heat when burned in air.