NIC Esthetician Written ExamScientific ConceptsHard
An esthetician is preparing to perform a chemical peel with a pH of 2.5. Understanding the acid-base balance, if the skin's natural pH averages 5.5, what is the approximate difference in acidity measured on the logarithmic pH scale between the peel and healthy skin?
- A100 times more acidic
- B1,000 times more acidic
- C3 times more acidic
- D30 times more acidic
Show answer & explanationAnswer & explanation
Correct answer: B. 1,000 times more acidic
The pH scale is logarithmic, meaning each whole number change represents a tenfold difference in acidity or alkalinity. A difference of 3 pH units (5.5 - 2.5 = 3) means the peel is 10^3, or 1,000 times more acidic than the skin.
Why the other options are wrong
- A. This would be a difference of 2 pH units (10^2), not 3 pH units.
- C. This would be a difference of 0.5 pH units, or 10^0.5, which is approximately 3.16 times, not a whole 3 pH units difference.
- D. This would be a difference of 1.5 pH units, or 10^1.5, which is approximately 31.6 times, not 3 whole pH units difference.
pH Scale Logarithmic Nature
The pH scale is logarithmic, meaning each whole number change represents a tenfold difference in acidity or alkalinity, not a linear difference.
- Scale from 0-14
- 7 is neutral
- Each unit is 10x difference
Memory trick: Each pH step is a TEN-fold jump, like taking a power of 10.