Question

Consider the following equilibrium:

4Fe(s) + 3 O2(g) <-- --> 2Fe2O3(s);

Which of the following equations is wrong?
Kp=Kc(RT)-5
Kc=[O2]-3
Kp= Kc(RT)-3
Kp = PO2-3

Answer 1

Answer: The equation which is wrong is
`K_p=K_c(RT)^(-5)`

Step-by-step explanation:

For the given reaction:

`4Fe(s)+3O_2(g)\rightarrow 2Fe_2O_3(s)`

The expression for
`K_c\text{ and }K_p` is given by:

`K_c=(1)/([O_2]^3)`

`K_p=(1)/([O_2]^3)`

The concentration of solids are taken to be 1, only concentration of gases and liquid states are taken. The pressure of only gases are taken.

Relationship between
`K_p\text{ and }K_c` is given by the expression:

`K_p=K_c* (RT)^(\Delta n_g)`

where,

`\Delta n_g`= number of moles of gaseous products - number of moles of gaseous reactants

R = gas constant

T= temperature

For the above reaction,

`\Delta n_g` = number of moles of gaseous products - number of moles of gaseous reactants = 0 - 3 = -3

Hence, the expression for
`K_p` is:

`K_p=K_c* (RT)^(-3)`

Therefore, the equation which is wrong is
`K_p=K_c(RT)^(-5)`