Mixture concentration average – UGC NET Question

This option is correct because when equal quantities are mixed, the concentration of the mixture is the simple average of the two concentrations. The average of 10% and 20% is (10 + 20)/2 = 15%. Since both quantities are equal, no other weighting is needed. Therefore, the resulting concentration is 15%.

Option A:
If the mixture concentration remained at 10%, the presence of the stronger 20% solution would have no effect. This contradicts the idea of mixing. Therefore, 10% cannot be the concentration after mixing equal amounts.

Option B:
When equal volumes are combined, each solution contributes equally to the final concentration. Averaging 10% and 20% gives 15%, which lies between the two original values. This matches our expectation for a mixture of equal parts, so 15% is correct.

Option C:
A concentration of 20% would ignore the dilution effect of the weaker 10% solution. The final concentration cannot be as high as the stronger solution when they are mixed equally. Thus, 20% is not correct.

Option D:
30% exceeds both of the original concentrations. Mixing cannot produce a concentration stronger than the strongest component without adding extra solute. Therefore, 30% is impossible in this context.