What is the molecular weight of Sodium Hydroxide (NaOH)?

Appeared in: AIIMS CRE, SNO-2024

Explanation

The molecular weight of a compound is calculated by summing the atomic weights of all the atoms in its formula.
The chemical formula for Sodium Hydroxide is NaOH.
The atomic weight of Sodium (Na) is approximately 23 g/mol.
The atomic weight of Oxygen (O) is approximately 16 g/mol.
The atomic weight of Hydrogen (H) is approximately 1 g/mol.
Summing these values gives the molecular weight: 23 + 16 + 1 = 40 g/mol.

Option A: This value represents the atomic weight of only the Sodium (Na) atom, not the entire NaOH molecule.
Option B: This value is the approximate atomic weight of Chlorine (Cl), which is not a component of Sodium Hydroxide.
Option D: This value represents the approximate molecular weight of Sodium Chloride (NaCl), a different chemical compound (23 for Na + 35.5 for Cl ≈ 58.5).

Visual 1: Diagram - A simple graphic showing the chemical formula NaOH breaking down into its components (Na, O, H) with their respective atomic weights (23, 16, 1) and then being summed up to 40.
Visual 2: Table - A section of the periodic table highlighting the elements Sodium (Na), Oxygen (O), and Hydrogen (H) with their atomic masses clearly displayed.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Calculation of molecular weight from a chemical formula as background academic context rather than a clinical decision trigger.
While calculating molecular weight is a chemistry concept, understanding the properties of chemicals like Sodium Hydroxide (NaOH) is critical for nurse safety and patient care, especially in cases of accidental exposure.
NaOH is a caustic agent found in many household cleaners. Nurses must be able to educate patients on safe storage and be prepared to manage exposures, which are medical emergencies.
What if? - If a patient ingests NaOH instead of a skin exposure, the priority action changes. The focus is on securing the airway (due to risk of swelling) and preparing for emergency endoscopy. Inducing vomiting is strictly contraindicated as it would re-expose the esophagus to the caustic agent, worsening the injury.

How to Approach the Question

First, identify the chemical formula provided in the question, which is Sodium Hydroxide (NaOH).
Break down the formula into its individual elements: Sodium (Na), Oxygen (O), and Hydrogen (H).
Recall the approximate atomic weight for each of these common elements from the periodic table.
Sum the atomic weights of all the atoms in the formula: Atomic Weight of Na + Atomic Weight of O + Atomic Weight of H.
Calculate the total: 23 + 16 + 1 = 40.
Compare your calculated total with the given options to find the correct answer.

Concept Tested & Keywords

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E6 Nutrition Kumud Khanna 2e p. 223-227

Practise the full AIIMS CRE, SNO-2024

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