Concentration unit definition: The number of gram-moles of solute dissolved per litre of solution is called…
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Aequivalent weight
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Bmolarity
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Cmolality
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Dnormality
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Eformality
Answer
Correct Answer: molarity
Explanation
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:
Molarity M = n_solute / V_solution(L).Molality m = n_solute / mass_solvent(kg).Normality N = equivalents / litre (context-dependent on reaction).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