calculate the amount of heat evolved in the complete oxidation of 8.17g of Al at 25 degrees C and 1 atm pressure. change in H for Al2O3 is -1676kJ/mol.
4Al(s) + 3O2(g)--> 2Al2O3(s)
please giv me the steps to solving this
thanx.
delta H = -1676 kJ/mol
How many mols do you have?
mols = g/molar mass = 8.17 g Al/27 =??
??mols x -1676 kJ/mol = xx kJ.
I rounded for the atomic mass of Al; I think it is 26.98 and you should look up the actual value and use that number instead of my rounded number.
254
Step 1: Find the number of moles of Al
To find the number of moles of Al, use the formula:
mols = mass/molar mass
mols = 8.17g / 27g/mol (rounded atomic mass of Al) = 0.303 mol
Step 2: Calculate the heat evolved
Use the equation:
ΔH = n × ΔH_
Where:
ΔH = change in enthalpy (-1676 kJ/mol)
n = number of moles (0.303 mol)
ΔH = 0.303 mol × -1676 kJ/mol
ΔH = -507.828 kJ
Therefore, the amount of heat evolved in the complete oxidation of 8.17g of Al is -507.828 kJ.
To calculate the amount of heat evolved in the complete oxidation of 8.17g of Al, you need to follow these steps:
Step 1: Determine the number of moles of Al.
Use the formula: moles = mass/molar mass.
Given mass of Al = 8.17g.
Molar mass of Al = 27g/mol (rounded value).
moles of Al = 8.17g/27g/mol ≈ 0.302 mol.
Step 2: Use the balanced chemical equation to determine the molar ratio.
From the balanced equation: 4 Al + 3 O2 → 2 Al2O3.
The ratio between Al2O3 and Al is 2:4 (or 1:2).
Therefore, moles of Al2O3 = moles of Al/2 ≈ 0.151 mol.
Step 3: Calculate the amount of heat evolved.
Use the equation: ΔH = moles × ΔH per mole.
Given: ΔH per mole of Al2O3 = -1676 kJ/mol.
ΔH = 0.151 mol × -1676 kJ/mol = -252.776 kJ.
So, the amount of heat evolved in the complete oxidation of 8.17g of Al is approximately -252.776 kJ.