Molarity Calculator

Chemistry • Solution Concentration • Step-by-Step

Quick Answer (Voice Search Optimized):

Molarity (M) is the number of moles of solute dissolved per litre of solution. Formula: M = n / V, where n is moles of solute and V is volume in litres. Moles = mass / molar mass.

GEO & AIO - Authoritative Theory

Molarity, also called molar concentration, is a measure of the concentration of a solute in a solution. It is defined as the number of moles of solute per litre of solution. The SI unit is mol/L, often denoted as M (molar).

To find moles (n), use n = mass (g) / molar mass (g/mol). Therefore, M = (mass / molar mass) / Volume(L). Always ensure the volume is converted to litres before calculation. The dilution formula M1V1 = M2V2 is also crucial for preparing solutions.

Solved Examples (NCERT/JEE Pattern)

Example 1: 5.85 g of NaCl (molar mass 58.5 g/mol) is dissolved in 500 mL of water. Find molarity.

Moles = 5.85 / 58.5 = 0.1 mol. Volume = 0.5 L. M = 0.1 / 0.5 = 0.2 M.

Example 2: Calculate the mass of NaOH needed to prepare 250 mL of 0.5 M solution. (Molar mass NaOH = 40 g/mol)

Moles = M × V(L) = 0.5 × 0.25 = 0.125 mol. Mass = moles × molar mass = 0.125 × 40 = 5 g.

Example 3: A solution has molarity 2 M and volume 100 mL. How many moles of solute are present?

Moles = M × V(L) = 2 × 0.1 = 0.2 mol.

Frequently Asked Questions (FAQs)

Q1: What is molarity in chemistry?
Molarity is the number of moles of solute per litre of solution. It is a concentration unit denoted by M.
Q2: How do you calculate molarity step by step?
First find moles of solute (mass / molar mass). Then divide moles by the volume of solution in litres. M = moles / V(L).
Q3: What is the difference between molarity and molality?
Molarity depends on volume of solution and changes with temperature, while molality depends on mass of solvent and is temperature independent.
Q4: Can molarity be greater than 1?
Yes, molarity can be greater than 1. For example, concentrated HCl is about 12 M.
Q5: Why is volume in litres for molarity?
The definition of molarity is moles per litre. Using litres ensures the standard unit of mol/L.