Concept:The dimensional units of the equilibrium constant \( K_c \) are dictated by the net change in stoichiometry (moles) of the balanced equation.
Formula:$$ \text{Units of } K_c = (\text{mol/dm}^3)^{\Delta n} $$
Solution:- \( \Delta n \) equals the moles of products minus the moles of reactants.
- If the moles of products are exactly equal to reactants, then \( \Delta n = 0 \).
- Substituting zero into the formula gives \( (\text{mol/dm}^3)^0 \).
- Since any non-zero term raised to the zeroth power is 1, the dimensional units completely cancel out, leaving the constant unitless.
Why other options are incorrect:If products are more or less than reactants, \( \Delta n \) is non-zero, meaning standard molarity units will remain raised to a positive or negative power.
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