What is the pH of a solution with a H+ ion concentration of 1 x 10^-4

A logarithmic scale condenses the range of acidity to numbers that are easy to use. Consider a solution with [H + ] = 1.0 × 10 -4 M. That is a hydrogen-ion concentration that is 1000 times higher than the concentration in pure water. The pH of such a solution is 4.00, a difference of just 3 pH units.

the correct answer is b

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.