Thermite mixtures are used for certain types of weldings and the thermite reaction is highly exothermic. Given delta H= -852 KJ/mol, 1 mole of granular Fe2O3 and 2 moles of granular aluminum are mixed at room temperature and the reaction is initiated. the liberated heat is retain within the products whose combined specific heat over a broad temperature range is about 0.8 J/g C . the melting pt. of Fe is 1530 C. show that the quantity heat liberated is more than sufficient to raise the temp. of the products to the melting pt. of Fe.
Fe2O3 + 2Al - Al203 + 2Fe
To determine if the quantity of heat liberated is sufficient to raise the temperature of the products to the melting point of Fe (1530°C), we need to calculate the total heat liberated and compare it to the heat required to raise the temperature.
First, we need to calculate the heat liberated in the reaction using the enthalpy change (ΔH) value given. The enthalpy change for the reaction is ΔH = -852 kJ/mol.
Next, we need to calculate the number of moles of Fe2O3 and Al used in the reaction. We are given that 1 mole of Fe2O3 and 2 moles of Al are used.
The total heat liberated in the reaction can be calculated using the equation:
Heat liberated = ΔH * number of moles of reaction
Heat liberated = -852 kJ/mol * (1 mole of Fe2O3 + 2 moles of Al)
Next, we need to convert the calculated heat liberated from kJ to J, as the specific heat is given in J/g°C.
1 kJ = 1000 J
Therefore,
Heat liberated = -852 kJ/mol * (1 mole of Fe2O3 + 2 moles of Al) * (1000 J/kJ)
Now, to determine if this heat is sufficient to raise the temperature of the products to the melting point of Fe, we need to calculate the heat required to raise the temperature.
The specific heat capacity of the products is given as 0.8 J/g°C.
To calculate the heat required to raise the temperature, we need to know the mass of the products formed. Since the reaction stoichiometry is 1 mole of Fe2O3 and 2 moles of Al, it means that 1 mole of Al2O3 and 2 moles of Fe are formed.
To calculate the mass of the products formed, we need to know the molar mass of Al2O3 and Fe.
The molar mass of Al2O3 can be calculated as follows:
Al: 2(26.98 g/mol) = 53.96 g/mol
O: 3(16.00 g/mol) = 48.00 g/mol
Molar mass of Al2O3 = 53.96 g/mol + 48.00 g/mol = 101.96 g/mol
Since 1 mole of Al2O3 is formed, the mass of Al2O3 = 101.96 g/mol.
The molar mass of Fe can be calculated as follows:
Fe: 2(55.85 g/mol) = 111.70 g/mol
Since 2 moles of Fe are formed, the mass of Fe = 111.70 g/mol * 2 = 223.40 g.
Therefore, the total mass of the products formed = Mass of Al2O3 + Mass of Fe = 101.96 g + 223.40 g = 325.36 g.
Now, we can calculate the heat required to raise the temperature using the equation:
Heat required = Mass of products * Specific heat * Temperature change
Temperature change = Melting point of Fe - Room temperature
Temperature change = 1530°C - 25°C (assuming room temperature is 25°C)
Now we substitute the values into the equation:
Heat required = 325.36 g * 0.8 J/g°C * (1530°C - 25°C)
Finally, we compare the calculated heat liberated to the heat required. If the heat liberated is greater than the heat required, then the quantity of heat liberated is more than sufficient to raise the temperature of the products to the melting point of Fe.