Colorado Cosmetology Written Practice Exam

What is the pH of sodium hydroxide?

1. 1.5-2.5

2. 4.5-5.5

3. 10.5-11.5

4. 12.5-13.5

The correct answer is: 1.5-2.5

Sodium hydroxide, commonly known as lye, is a strong alkaline substance that has a very high pH level. Its pH typically ranges from 12.5 to 13.5, which places it firmly in the category of caustic alkalis. This high pH is why it is effective in various applications, such as in hair smoothing treatments and chemical peels, as it can alter the structure of hair and skin. Understanding the nature of sodium hydroxide is important, particularly in the context of its uses in cosmetology. This knowledge helps explain the handling precautions necessary to prevent chemical burns and skin irritation. The options that suggest much lower pH levels indicate either acidic or neutral substances, which do not accurately represent sodium hydroxide's properties. Hence, the correct answer is the one that correctly identifies the high pH of sodium hydroxide.