Q.39 Molarity is a better way of expressing the concentration of solution as compared to gram percent especially
1. under all conditions
2. for anhydrous molecules
3. for molecules with different hydrated states
4. for all solids and liquids
Molarity expresses solution concentration as moles of solute per liter of solution, offering advantages over gram percent (mass solute per 100g solution) by accounting for molecular weight and particle number, especially when hydration varies.
Correct Answer
3. for molecules with different hydrated states
Gram percent ignores hydration differences (e.g., anhydrous CuSO4 vs. CuSO4·5H2O), leading to inconsistent molar amounts; molarity normalizes to moles regardless of water content, ensuring stoichiometric accuracy.
Option Analysis
Under All Conditions (Option 1)
False: Gram percent suffices for simple mass-based needs (e.g., NaCl solutions); molarity adds volume dependency, unnecessary for non-reactive contexts.
For Anhydrous Molecules (Option 2)
No advantage: Both methods work equally for non-hydrated solutes like glucose, as no water mass confounds gram percent.
For Molecules with Different Hydrated States (Option 3)
Correct: Hydrates have varying formula masses (e.g., 5% MgSO4 vs. MgSO4·7H2O yields different moles); molarity specifies true solute particles.
For All Solids and Liquids (Option 4)
Overbroad: Liquids (e.g., ethanol) use volume percent better; molarity excels specifically for hydration/equivalence issues.
| Option | Molarity Advantage? | Key Limitation of Gram % |
|---|---|---|
| All conditions | No | Volume irrelevant sometimes |
| Anhydrous molecules | Minimal | Equivalent performance |
| Different hydrated states | Yes | Varies moles falsely |
| All solids/liquids | No | Ignores phase specifics |
Clinical Relevance
In pharma/biochem (e.g., saline, buffers), molarity prevents dosing errors from hydrates; essential for NEET/CSIR calculations.
