Magnesia (MgO(s)) is used for fire brick, crucibles and furnace linings because of its high melting point. It is produced by decomposing magnesite (MgCO3(s)) into at around 1200oC
Write a balanced equation for the magensite decomposition being sure to include states for the species.
I thought it was:
MgCO3(s) ...> MgO (s) + CO2(g)
but it was marked wrong.
help..thank you.•Chemistry - DrBob222, Monday, November 9, 2015 at 12:46am
Probably I would have marked it right; it may be that you omitted the heat sign over the arrow OR the word "heat" on the left side.
It said hint:
When MgCo3 decomposes, MgO is one of the products. What is the other product? what formula could you use to calculate the change in enthalpy for a reaction if you had access to the molar enthalpies for each of the reactants and products? How could you use a similar strategy to calculate the change in enthalpy for a reaction?
thank you, Dr, BOB
They want you to show the heat in terms of kJ or perhaps kJ/mol.
MgCO3(s) + ?kJ ==> MgO(s) + CO2(g)
delta Hrxn = (n*dH products) - (n*dH reactants). dH rxn will be in terms of kJ/mol. I don't see any numbers in your post that would indicate the amount of MgCO3 you are starting with. In the absence of such data I would just write in whatever kJ/mol. If you have the data, then calculate the kJ based on the amount of MgCO3 used and use that for whatever kJ (without the mol).
The correct balanced equation for the decomposition of magnesite is:
MgCO3(s) → MgO(s) + CO2(g)
It seems like you have the right balanced equation. It's possible that you were marked wrong due to missing the heat sign over the arrow or the word "heat" on the left side. The addition of heat is needed for this decomposition reaction to occur.
As for the other product, it is carbon dioxide (CO2) in the gaseous state.
To calculate the change in enthalpy (ΔH) for a reaction, you can use the enthalpy values (in this case, the molar enthalpies) of the reactants and products. The formula to calculate ΔH is:
ΔH = ΣΔH(products) - ΣΔH(reactants)
Where Σ indicates the sum of the enthalpies of the reactants and products.
To calculate ΔH, you need to know the molar enthalpies (ΔH) for each species involved in the reaction. This information can often be found in reference tables or calculated using experimental data.
Using a similar strategy, you can calculate the change in enthalpy for other reactions by summing the molar enthalpies of the products and subtracting the sum of the molar enthalpies of the reactants.