Which of the following is the range of the pH scale?

Appeared in: NHM UP Staff Nurse - 2017

Explanation

The standard pH scale is a measure of acidity or alkalinity that ranges from 0 to 14.
A pH of 7 is neutral, values below 7 are acidic, and values above 7 are alkaline (basic).
The scale is logarithmic, meaning each whole pH value below 7 is ten times more acidic than the next higher value.
A pH of 0 represents the highest concentration of hydrogen ions (strongest acid), while a pH of 14 represents the lowest (strongest base).

Option B: This range is incorrect because it excludes very strong acids, which can have a pH between 0 and 1.
Option C: This range is incorrect as it omits strong alkaline substances, which can have a pH up to 14 (e.g., drain cleaner, bleach).
Option D: This range is incorrect because it only includes the acidic and neutral portions of the scale, completely leaving out the alkaline (basic) range from above 7 to 14.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Range of the pH scale as background academic context rather than a clinical decision trigger.
Understanding the pH scale is fundamental for interpreting Arterial Blood Gas (ABG) results, which are critical for diagnosing and managing a patient's acid-base balance.
Normal arterial blood pH is tightly regulated between 7.35 and 7.45. A pH below 7.35 indicates acidosis, and a pH above 7.45 indicates alkalosis. Both can be life-threatening.
What if? If a patient's blood pH drops to 7.20, they are in a state of acidosis. The nurse's priority would be to assess the patient's respiratory status and level of consciousness, notify the physician immediately, and prepare for interventions like administering sodium bicarbonate or adjusting ventilation, depending on the cause.

How to Approach the Question

This is a factual recall question that tests foundational knowledge in chemistry and physiology.
First, identify the core concept being asked: the complete numerical range of the pH scale.
Recall the standard scientific definition of the pH scale, which is used to measure the full spectrum from highly acidic to highly alkaline substances.
Evaluate each option against this definition. The scale must include the strongest acids (starting at 0), the neutral point (7), and the strongest bases (ending at 14).
Eliminate options that represent an incomplete or incorrect range, such as those that cut off the acidic or basic ends.

Concept Tested & Keywords

QUzZ6NLcOblNiJf_qonV4Z

E6 Physiology Guyton 4SAE Part 2B p. 66-68

E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 54-56

E6 Physiology Ganong 27e Vol 1 Part 1 p. 13-15

Practise the full NHM UP Staff Nurse - 2017

Attempt every question from this paper in a timed mock, then review the full solution for each one.