The pH of healthy human blood is best described as which of the following?

Introduction / Context:
The pH scale is used to describe how acidic or basic a solution is. Human blood has a tightly regulated pH, and understanding whether it is acidic or basic helps connect chemistry with human physiology. Small deviations from the normal range can have serious health consequences, so this is also an important point in biology and medical entrance examinations.

Given Data / Assumptions:

• Typical healthy arterial blood pH is about 7.35 to 7.45.
• On the pH scale, 7 is neutral, values below 7 are acidic, and values above 7 are basic or alkaline.
• The options ask us to choose slightly acidic, highly acidic, slightly basic, or highly basic.

Concept / Approach:
Since blood pH lies slightly above 7, it must be on the basic side. However, the difference from neutrality is small, so it is not correct to say highly basic. Instead, we classify blood as slightly basic or slightly alkaline. The body maintains this narrow range through buffer systems like bicarbonate, haemoglobin, and phosphate buffers, as well as respiratory and renal regulation.

Step-by-Step Solution:
Step 1: Recall the normal pH range of human blood. It is approximately 7.35 to 7.45. Step 2: Compare this range with neutral pH. Neutral pH is 7.0, so blood pH is slightly greater than 7. Step 3: Decide on acidity or basicity. Any solution with pH greater than 7 is basic or alkaline, while pH less than 7 would be acidic. Since blood pH is only slightly above 7, it must be slightly basic.

Verification / Alternative Check:
Medical references define acidosis as a condition where blood pH tends to fall below the normal range, that is, below 7.35, and alkalosis where pH increases above 7.45. Both are considered abnormal, reinforcing that the healthy baseline is a slightly basic region centred around 7.4. This confirms that describing blood as slightly basic is correct, whereas calling it acidic or highly basic does not match observed values.

Why Other Options Are Wrong:
Option A: Slightly acidic would imply pH just below 7, which is not consistent with measured values of normal blood. Option B: Highly acidic would correspond to much lower pH values, such as 1 or 2, which would be incompatible with life. Option D: Highly basic would imply a pH value far above 7, such as 10 or 12, again impossible for normal physiology.

Common Pitfalls:
Some learners mistakenly assume that blood must be neutral because it is so important to the body, or they confuse the idea that the stomach is acidic with the condition of blood. Others misremember the pH range and think 7.0 is the exact value. Careful attention to diagrams and tables in textbooks, which usually show blood at pH 7.4, helps avoid such confusion.

Final Answer:
The pH of human blood is Slightly Basic.