What term describes a measure of acidity with a scale of 1 to 14?

• A. pH
• B. Haemoglobin
• C. Myoglobin
• D. Mitochondria

Answer: (A)

Measuring acidity is about pH, a term that describes how acidic or basic a solution is. pH is calculated as the negative logarithm of the hydrogen ion concentration, so it reflects how many H+ ions are present. The scale runs from 1 to 14 in typical aqueous solutions, with 7 being neutral; values below 7 indicate acidity and higher values indicate basicity. The lower the pH, the stronger the acidity; each unit represents a tenfold change in hydrogen ion concentration. In the body, for example, blood has to stay within a narrow pH range (about 7.35–7.45) to keep enzymes working properly. The other terms listed—haemoglobin, myoglobin, mitochondria—are not measures of acidity: haemoglobin and myoglobin are proteins involved in oxygen transport and storage, while mitochondria are organelles for energy production.