But you need to manipulate the equations and arrive at the etropy through addition / subtraction / multiplication / division of the dG.

Again, until I can get home and pull out text books, I hesitate to go further.

(Its been awhile).

Solved

Posted on 2007-08-06

how to calculate the DG for CACO3 given :

c+ 02 -- c02 DG = -394.4 kj

CaO + CO2 -- CaCO3 DG = -130.4 kj

Ca + 1/2 O2 -- CaO DG = - -604 Kj

the answers given :

a. -1128.8 kj

b. -340 kj

c. -130.4 kj

d. 868 kj

e. 1128.8 kj

any ideas ?

c+ 02 -- c02 DG = -394.4 kj

CaO + CO2 -- CaCO3 DG = -130.4 kj

Ca + 1/2 O2 -- CaO DG = - -604 Kj

the answers given :

a. -1128.8 kj

b. -340 kj

c. -130.4 kj

d. 868 kj

e. 1128.8 kj

any ideas ?

11 Comments

But you need to manipulate the equations and arrive at the etropy through addition / subtraction / multiplication / division of the dG.

Again, until I can get home and pull out text books, I hesitate to go further.

(Its been awhile).

http://en.wikipedia.org/wi

-- Been to long for me, need my old texts...

Being homework on your end:

You know the end result is reactants = CaCO3

Hence:

C + O2 --> CO2

CaO + CO2 --> CaCO3

Ca + 1/2 O2 --> CaO

The CaO's cancel out

the CO2 cancel out

Take the link and run with it... You'll use the dG's supplied to calculate the new equation.

--> Sorry, but EE policy does not allow Experts to provide solutions to homework.

What were your starting components?

ie were your starting components CA, C, and O or CaO, CO2, or?

They are given the equations provided, and through cancelation (and in some cases) manipulation of the equations and G given for equation, arrive at the needed equation and G for new equation.

C + O2 + Ca + 1/2 O2 --> CaCO3

If memory serves, then use the dG for equation against values found in table (back of Chem text) for an explicit value for CaCO3.

After all ... you need to learn the material! :-)

CaO + CO2 --> CaCO3 DG = -130.4 kj

Ca + 1/2 O2 --> CaO DG = - -604 Kj

Ca + .5 O2 + C + O2 -> CaCO3

=-604kJ + -394.4kJ - -130.4 kJ ====> 340kJ

Granted I haven't had chemistry in 4years, but I can make stuff up!

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