When calculating the equilibrium constant, aqueous solutes must be expressed in moles per liter (M). and gases must be expressed in pressure as bars. This is because A. there are no other ways to express pressure or concentration other than bars or moles per liter (M). B. they are dimensionless ratios of the actual concentration or pressure divided by standard state concentration, which is 1 M for solutions and 1 bar for gases. C. these are the only units of concentration and pressure that are independent of temperature. D. the dimensionless ratios are always unity (1) because the concentration of the solute or pressure of the gas are divided by standard state concentrations.