Chemistry · Some Basic Concepts Of Chemistry · NEET
M1 and V1 are the molarity and volume of the solution BEFORE you add water. M2 and V2 are the molarity and volume AFTER you add water. The equation says: moles before = moles after. Since moles = Molarity x Volume, and moles do not change during dilution, M1V1 must equal M2V2. That is the whole idea.
When you dilute, you only add solvent (water). You do not add or remove any solute. So the same number of solute particles is now spread through more liquid. The moles stay constant; only the volume grows and the molarity drops. This is the single most important point for NEET dilution problems.
It changes MOLARITY (it goes down) but NOT the moles of solute (they stay the same). Many students mix this up. Remember: adding water lowers concentration but never changes how much solute you have.
V1 and V2 must be in the SAME unit (both in mL, or both in L). Because volume appears on both sides, the units cancel, so you do not have to convert to litres. Just keep them matching. M1 and M2 are both in mol/L (molarity).
They are actually the same idea. n = M x V gives you the moles in one solution. M1V1 = M2V2 just says the moles (M x V) are equal before and after dilution. So the dilution formula is n = M x V applied twice, with the moles set equal.
Rearrange the formula: V2 = (M1 x V1) / M2. Then the amount of WATER you added is V2 minus V1. Careful: the formula gives the FINAL total volume, not the water added. Subtract to get the water.
Yes. M1V1 = M2V2 works for any dilution where you only add solvent, including diluting concentrated HCl or H2SO4. It also works with normality (N1V1 = N2V2) and even mass problems, as long as the amount of solute is conserved.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The dilution formula is M1V1 = M2V2, where M1 and V1 are molarity and volume before dilution, and M2 and V2 are molarity and volume after adding water. It works because moles of solute stay constant.
Only that V1 and V2 use the same unit. Both in mL or both in L is fine, because the volume units cancel across the equation. No conversion to litres is needed.
Use M2 = (M1 x V1) / V2 = (2 x 100) / 500 = 0.4 M. The concentration dropped from 2 M to 0.4 M, but the moles (0.2 mol) stayed the same.
They follow the same logic. M1V1 = M2V2 uses molarity for simple dilution; N1V1 = N2V2 uses normality and is common in titrations and acid-base neutralisation problems.
NEET Chemistry regularly gives numericals where water is added to a solution or two solutions are mixed. M1V1 = M2V2 lets you solve these fast without recalculating moles from scratch, saving time in the exam.
