Molar Mass Calculator Of Unknown Solution

Molar Mass Equation:

\[ MW = \frac{\Delta T_f \times K_f \times 1000 \times m_{solute}}{kg_{solvent}} \]

Freezing Point Depression (ΔT_f):

°C

Cryoscopic Constant (K_f):

°C kg/mol

Mass of Solute:

Mass of Solvent:

Molar Mass (MW):

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1. What is Molar Mass of Unknown Solution?

The molar mass of an unknown solution can be determined using freezing point depression, a colligative property that depends on the number of solute particles in solution. This method is particularly useful for determining the molecular weight of unknown compounds.

2. How Does the Calculator Work?

The calculator uses the freezing point depression equation:

\[ MW = \frac{\Delta T_f \times K_f \times 1000 \times m_{solute}}{kg_{solvent}} \]

Where:

\( MW \) — Molar mass (g/mol)
\( \Delta T_f \) — Freezing point depression (°C)
\( K_f \) — Cryoscopic constant (°C kg/mol)
\( m_{solute} \) — Mass of solute (g)
\( kg_{solvent} \) — Mass of solvent (kg)

Explanation: The freezing point depression is proportional to the molality of the solution, which allows calculation of the solute's molar mass.

3. Importance of Molar Mass Calculation

Details: Determining molar mass is fundamental in chemistry for identifying unknown compounds, calculating stoichiometric relationships, and understanding solution properties.

4. Using the Calculator

Tips: Enter all values in the correct units. The freezing point depression should be measured precisely, and the cryoscopic constant should be appropriate for your solvent (e.g., 1.86 °C kg/mol for water).

5. Frequently Asked Questions (FAQ)

Q1: What solvents can be used with this method?
A: Common solvents include water, benzene, and cyclohexane. Each has its own cryoscopic constant (K_f).

Q2: What are typical values for freezing point depression?
A: For aqueous solutions, typical ΔT_f values range from 0.1°C to 5°C depending on solute concentration.

Q3: What are limitations of this method?
A: The solute must be non-volatile and non-electrolyte. For electrolytes, the van't Hoff factor must be considered.

Q4: How accurate is this method?
A: With careful measurement, accuracy within 5% can be achieved for compounds with MW between 100-1000 g/mol.

Q5: Can this be used for polymer solutions?
A: Yes, but results may represent average molecular weights due to polydispersity in polymer samples.