Concentration unit definition: The number of gram-moles of solute dissolved per litre of solution is called…

Introduction / Context:Different analytical and process problems call for different concentration measures. Molarity is ubiquitous in laboratory work and reaction-rate expressions because it references the actual solution volume at the condition of interest.

Given Data / Assumptions:

• Molarity (M) = moles of solute per litre of solution.
• Other units exist (molality, normality, formality) and should not be confused with molarity.
• Temperature can change solution volume, hence molarity can be temperature-dependent.

Concept / Approach:Identify the unit that matches “gram-moles per litre of solution.” This maps directly to molarity. Molality uses kilograms of solvent; normality uses equivalents per litre; equivalent weight is not a concentration unit.

Step-by-Step Clarification:

Verification / Alternative check:Check typical notations: 1.0 M HCl means 1 mole HCl in each litre of final solution volume, consistent with the definition.

Why Other Options Are Wrong:

• Equivalent weight: Property of a substance, not a concentration unit.
• Molality/Normality/Formality: Do not match the “per litre of solution” wording.

Common Pitfalls:Interchanging molarity and molality; ignoring temperature effects on solution volume when high precision is needed.

Final Answer:molarity