# Which of the following equilibriums most favours the reactants and why?a) NO+1/2O2=NO2 Keq=4.4x10^7 b) CO+1/2O2=CO2 Keq=4.0x10^-3 c) C+H2O=CO+H2 Keq 3.1x10^3 d) NO+H2O=NO2+H2 Keq 1.0x10^-22

justaguide | College Teacher | (Level 2) Distinguished Educator

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For any chemical reaction, aA + bB --> cC + dD, the equilibrium constant Keq is equal to ({C}^c*{D}^d)/({A}^a*{B}^b) where {} denotes the concentration of the respective reactants and products.

As the value of Keq decreases the rate of the forward reaction decreases and that of the backward reaction increases. Equilibrium is then reached at a smaller concentration of the products formed compared to the concentration of the reactants.

Here, it is seen that the lowest value of Keq is for the reaction NO+H2O --> NO2 + H2 where Keq is only 1.0x10^-22

For this particular reaction equilibrium is reached when a very small amount of the reactants have been converted to the product. This value for the equilibrium constant most favors the reactants.

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