Using standard enthalpies information, calculate the standard enthalpy change for this reaction.
a)(thermite reaction) 2Al(s) + Fe2O3(s) = Al2O3(s) + 2Fe(s)
b)Mg(OH)2(s) = MgO(s) + H2O(I)
c)N2O4(g) + 4H2(g) = N2(g) + 4H2O(g)
d)SiCl4(I) + 2H2O(I) = SiO2(s) + 4HCI(g)
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a) To calculate the standard enthalpy change for the reaction 2Al(s) + Fe2O3(s) = Al2O3(s) + 2Fe(s), we can use the standard enthalpy of formation values for the compounds involved.
The standard enthalpy of formation for Al(s) is 0 kJ/mol, Fe2O3(s) is -824.2 kJ/mol, Al2O3(s) is -1675.7 kJ/mol, and Fe(s) is 0 kJ/mol.
The standard enthalpy change for the reaction can be calculated using the formula:
ΔH = Σ(nΔH_f(products)) - Σ(nΔH_f(reactants))
where ΔH is the standard enthalpy change, n is the stoichiometric coefficient, and ΔH_f is the standard enthalpy of formation.
In this case:
ΔH = [2(0 kJ/mol) + 2(-1675.7 kJ/mol)] - [2(-824.2 kJ/mol) + 0 kJ/mol]
= -3351.4 kJ/mol + 1648.4 kJ/mol
= -1703 kJ/mol
Therefore, the standard enthalpy change for the reaction is -1703 kJ/mol.
b) To calculate the standard enthalpy change for the reaction Mg(OH)2(s) = MgO(s) + H2O(I), we can use the standard enthalpy of formation values.
The standard enthalpy of formation for Mg(OH)2(s) is -924.3 kJ/mol, MgO(s) is -601.7 kJ/mol, and H2O(I) is -285.830 kJ/mol.
Using the same formula as above:
ΔH = Σ(nΔH_f(products)) - Σ(nΔH_f(reactants))
ΔH = [-601.7 kJ/mol + (-285.830 kJ/mol)] - [-924.3 kJ/mol]
= -887.530 kJ/mol + 924.3 kJ/mol
= 36.77 kJ/mol
Therefore, the standard enthalpy change for the reaction is 36.77 kJ/mol.
c) To calculate the standard enthalpy change for the reaction N2O4(g) + 4H2(g) = N2(g) + 4H2O(g), we need the standard enthalpy of formation values.
The standard enthalpy of formation for N2O4(g) is 9.16 kJ/mol, N2(g) is 0 kJ/mol, and H2O(g) is -241.831 kJ/mol.
ΔH = Σ(nΔH_f(products)) - Σ(nΔH_f(reactants))
ΔH = [0 kJ/mol + 4(-241.831 kJ/mol)] - [9.16 kJ/mol + 4(0 kJ/mol)]
= -967.324 kJ/mol - 9.16 kJ/mol
= -976.484 kJ/mol
Therefore, the standard enthalpy change for the reaction is -976.484 kJ/mol.
d) To calculate the standard enthalpy change for the reaction SiCl4(I) + 2H2O(I) = SiO2(s) + 4HCl(g), we need the standard enthalpy of formation values.
The standard enthalpy of formation for SiCl4(I) is -657.8 kJ/mol, H2O(I) is -285.830 kJ/mol, SiO2(s) is -910.9 kJ/mol, and HCl(g) is -92.31 kJ/mol.
ΔH = Σ(nΔH_f(products)) - Σ(nΔH_f(reactants))
ΔH = [-910.9 kJ/mol + 4(-92.31 kJ/mol)] - [-657.8 kJ/mol + 2(-285.830 kJ/mol)]
= -1274.46 kJ/mol - (-1228.46 kJ/mol)
= -46 kJ/mol
Therefore, the standard enthalpy change for the reaction is -46 kJ/mol.
To calculate the standard enthalpy change for a reaction, you will need to use the standard enthalpy values of the reactants and products involved in the reaction. These values can be found in a standard enthalpy table.
a) To calculate the standard enthalpy change for the thermite reaction, you need to subtract the sum of the standard enthalpies of the reactants from the sum of the standard enthalpies of the products. The balanced equation for the reaction is:
2Al(s) + Fe2O3(s) -> Al2O3(s) + 2Fe(s)
The standard enthalpy change (∆H) can be calculated as follows:
∆H = [∑(∆H products)] - [∑(∆H reactants)]
Using the standard enthalpy values from the table, substitute the values into the equation and perform the calculation.
b) The balanced equation for the reaction is:
Mg(OH)2(s) -> MgO(s) + H2O(I)
Using the same method as in part (a), substitute the standard enthalpy values into the equation and perform the calculation.
c) The balanced equation for the reaction is:
N2O4(g) + 4H2(g) -> N2(g) + 4H2O(g)
Again, use the method described above to calculate the standard enthalpy change.
d) The balanced equation for the reaction is:
SiCl4(I) + 2H2O(I) -> SiO2(s) + 4HCl(g)
Follow the same procedure given above to calculate the standard enthalpy change for this reaction.
Remember to use the correct units for the standard enthalpies and ensure that the reactants and products are in the appropriate physical states (solid, liquid, gas) as listed in the enthalpy table.