Nonionic surfactants are effective at what pH range?

• A. >8
• B. 3-7
• C. 3-10
• D. 1-5

Answer: (C)

Nonionic surfactants are not ionizable, so their surface activity and micelle formation stay largely unchanged across a wide pH range. This pH independence means they remain effective from mildly acidic to moderately basic conditions. The commonly cited window of 3 to 10 covers acidic through basic environments, making them versatile in many formulations. Narrower ranges like above 8 miss the acidic end, while 1–5 misses the alkaline end, and 3–7 misses higher pH where nonionic surfactants still perform well. So 3–10 best represents the broad pH range over which nonionic surfactants remain effective.