N2(g) + 3 H2(g) <--> 2 NH3(g)
The concentrations of nitrogen gas, hydrogen gas, and ammonia gas are (4.7000x10^0) mol/L, (1.9000x10^0) mol/L and (9.00x10^-1) mol/L respectively. What is the value of the equilibrium constant? Answer to 3 S.D.
The equilibrium constant K is the ratio of the equilibrium concentrations of products to the product of the equilibrium concentrations of reactants, all raised to the power of their coefficients. For example, for this reaction
`N_2 + 3 H_2 -> 2NH_3`
the equilibrium constant expression is:
`K = ([(NH3)^2])/([N_2][(H_2)^3]`
The problem doesn't state that the concentrations given represent equilibrium conditions. Since these are the values given to solve the problem, I'll make that assumption.
K = (0.900)^2/(4.7000)(1.900)^3 = 0.0251
Notice that the units of (mol/L)^2(mol/L)/(mol/L)^3 , if included, would cancel out. Equilibrium constants don't have units for this reason.
The equilibrium constant is specific for a given temperature.
If the system isn't at equilibrium then the quantity calculated represents the reaction quotient Q. The concentrations of reactants and product will continue to change until equilibrium is established and Q=K.