Calculate the value of the standard enthalpy change for each of the following reactions (standard enthalpy for Na2SO4(s) is -1375.653 kj/mole):
a) 4HBr(g) + O2(g) = 2H2O(I) + 2Br(I)
b) 2Na(OH)(s) + SO3(g) = Na2SO4(s) + H2O(g)
c) CH4(g) + 4CI2(g) = CCI4(I) + 4HCI(g)
d) Fe2O3(s) + 6HCI(g) = 2FeCI3(s) + 2H2O(g)
See you last post.
dHrxn = (n*dHf products) - (n*dHf reactants)
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To calculate the standard enthalpy change for each of the given reactions, you'll need to use Hess's Law. According to Hess's Law, the total enthalpy change of a reaction is equal to the sum of the enthalpy changes of all the individual steps of the reaction.
Step 1: Write down the given balanced equation for each reaction.
a) 4HBr(g) + O2(g) = 2H2O(l) + 2Br(l)
b) 2Na(OH)(s) + SO3(g) = Na2SO4(s) + H2O(g)
c) CH4(g) + 4Cl2(g) = CCl4(l) + 4HCl(g)
d) Fe2O3(s) + 6HCl(g) = 2FeCl3(s) + 3H2O(g)
Step 2: Identify known standard enthalpy changes.
We are given that the standard enthalpy change for Na2SO4(s) is -1375.653 kJ/mol.
Step 3: Use Hess's Law to determine the standard enthalpy change for each reaction.
a) 4HBr(g) + O2(g) = 2H2O(l) + 2Br(l)
To find the enthalpy change for this reaction, we need to break it down into known reactions:
4HBr(g) = 4HCl(g) + 2Br(l) (Given: 4HBr)
2HCl(g) = H2(g) + Cl2(g) (Use known enthalpy changes or look up)
H2(g) + 1/2O2(g) = H2O(l) (Use known enthalpy changes or look up)
Add up the enthalpy changes of the individual steps:
4HBr(g) + O2(g) = 4HCl(g) + 2Br(l) (∆H1)
4HCl(g) = 2H2(g) + 2Cl2(g) (∆H2)
H2(g) + 1/2O2(g) = H2O(l) (∆H3)
The net reaction is obtained by adding all three equations:
4HBr(g) + O2(g) = 2H2O(l) + 2Br(l) (∆H1 + ∆H2 + ∆H3)
Repeat these steps for the other reactions b), c), and d) using known enthalpy changes or looking them up in reference material.
b) 2Na(OH)(s) + SO3(g) = Na2SO4(s) + H2O(g)
c) CH4(g) + 4Cl2(g) = CCl4(l) + 4HCl(g)
d) Fe2O3(s) + 6HCl(g) = 2FeCl3(s) + 3H2O(g)
Note: When adding/subtracting equations and their corresponding enthalpy changes, ensure that the stoichiometric coefficients are adjusted if needed.
By completing these steps, you can calculate the standard enthalpy change for each given reaction.