Which of the following is a property of an acid solution?
A. slippery to the touch
B. pH less than 7
C. turns red litmus paper blue
D. bitter taste
The correct answer and explanation is:
The correct answer is B. pH less than 7.
Acids are substances that, when dissolved in water, release hydrogen ions (H⁺), which lower the pH of the solution. A solution with a pH less than 7 is considered acidic. This is because the concentration of hydrogen ions is higher than in neutral water, which has a pH of 7. Acids exhibit several other characteristic properties, such as:
- Taste: Acids typically have a sour taste, as seen in citric acid found in lemons or acetic acid in vinegar.
- Reaction with metals: Acids can react with metals like zinc or magnesium to produce hydrogen gas.
- Effect on indicators: Acids turn blue litmus paper red, which is a simple test used to distinguish acids from bases. This is the reverse of what bases do, which is to turn red litmus paper blue.
- Electrical conductivity: Acids are good conductors of electricity because they produce free ions when dissolved in water. These ions allow the solution to carry an electrical current.
On the other hand, options A, C, and D describe properties associated with bases, not acids. Bases typically feel slippery to the touch, turn red litmus paper blue, and have a bitter taste. These properties are the opposite of acids. Bases have a pH greater than 7, whereas acids are always less than 7. Therefore, the defining property of an acidic solution is its pH being less than 7.