Molar Concentration Of Water Calculator

Molar Concentration of Water Formula:

\[ M = \frac{1000}{18.02} \approx 55.5 \text{ mol/L} \]

Molar Concentration (M):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Molar Concentration of Water?

The molar concentration of water represents the number of moles of water per liter of solution. For pure water at standard conditions, this is approximately 55.5 mol/L, calculated from water's density and molecular weight.

2. How Does the Calculator Work?

The calculator uses the molar concentration formula:

\[ M = \frac{\text{density} \times 1000}{\text{molecular weight}} \]

Where:

\( M \) — Molar concentration (mol/L)
density — Mass per unit volume (g/mL)
1000 — Conversion factor (mL to L)
molecular weight — Mass of one mole of substance (g/mol)

Explanation: The formula converts the mass concentration to molar concentration using the molecular weight of water.

3. Importance of Molar Concentration Calculation

Details: Understanding water's molar concentration is crucial for chemical equilibrium calculations, particularly in acid-base chemistry and reaction kinetics where water acts as both solvent and reactant.

4. Using the Calculator

Tips: For pure water, use default values (density = 1.0 g/mL, molecular weight = 18.015 g/mol). For other conditions or solutions, adjust these values accordingly.

5. Frequently Asked Questions (FAQ)

Q1: Why is the molar concentration of water approximately 55.5 mol/L?
A: This value comes from dividing water's density (1000 g/L) by its molecular weight (18.015 g/mol): 1000/18.015 ≈ 55.5 mol/L.

Q2: Does temperature affect water's molar concentration?
A: Yes, water's density changes with temperature, which affects its molar concentration. The 55.5 mol/L value is for water at 4°C where density is exactly 1.000 g/mL.

Q3: Can this calculator be used for aqueous solutions?
A: Yes, but note that adding solutes changes both density and effective molecular weight. For accurate results with solutions, use appropriate density and average molecular weight values.

Q4: Why is water's molar concentration important in chemical calculations?
A: In many chemical equilibria, water concentration appears in equilibrium constants. Its high and relatively constant concentration simplifies many calculations.

Q5: How does pressure affect water's molar concentration?
A: Pressure affects water's density slightly, which would change the molar concentration. However, for most practical purposes, the effect is negligible.