A logarathim question:
pH = – log h
The pH of a solution is dependent on the concentration of hydronium ions, h, and can be calculated by the equation above. If the concentration of hydronium in solution A is 100 times the concentration of the hydronium in solution B, what is the absolute value of the difference in their pH values?
Hmm…Is this ACT? Subject Test? Definitely not SAT with logs (not to mention 5 answer choices). No matter—I got you.
Easiest way to go here is just to plug in a couple values for the concentrations of solutions A and B. Let’s say A has a concentration of 1,000,000 and B has a concentration of 10,000. That meets the requirement of the question: the concentration of A is 100 times more than the concentration of B. Now just calculate both pH values (using log base 10 in case that’s not your calculator’s default):
And there you have your answer—the pH values are 2 apart. Don’t be fooled by choice A: the question asks for the absolute value of the difference so you definitely don’t want a negative number.