Volume to Moles Calculator (Pure Substances)
Convert the volume (in mL) of a known pure substance (element or compound, typically liquid or solid) into the amount of substance (in moles) using its density and molar mass.
Note: This calculator is for **pure substances** only. For solutions, please use the Molarity Calculator. For gases, properties depend on temperature and pressure (consider the Ideal Gas Law).
Enter Substance Properties
Converting Volume to Moles for Pure Substances
While volume (like milliliters, mL) measures space occupied, moles (mol) measure the actual amount of a substance (number of particles). You cannot directly convert between them without knowing how "dense" the substance is and how much a "mole" of it weighs.
This conversion requires two key properties of the **pure substance**:
- Density (ρ): Relates mass to volume ($\rho = \text{mass} / \text{volume}$). Common units are g/mL (grams per milliliter) or kg/L. Knowing the volume and density allows you to calculate the mass.
Step 1: Mass (g) = Density (g/mL) × Volume (mL) - Molar Mass (MM): The mass of one mole of the substance (in grams per mole, g/mol). This value is unique to each element or compound and is found by summing atomic weights from the periodic table. Knowing the mass and molar mass allows you to calculate the number of moles.
Step 2: Moles (mol) = Mass (g) / Molar Mass (g/mol)
This calculator combines these two steps to directly provide the moles from the volume input, given you provide the correct density and molar mass values.
When to Use This Calculator:
- Calculating the amount (moles) of a pure liquid reactant needed when measured by volume (e.g., using a graduated cylinder).
- Finding the moles present in a solid sample whose volume and density are known.
- Converting lab measurements between volume and amount of substance for pure chemicals.
- Essential tool in chemistry, material science, and related fields for quantitative analysis.
Remember this tool is **specifically for pure substances**, not mixtures or solutions (where concentration/molarity is used) or gases (where pressure and temperature are needed).
Examples with Step-by-Step Solutions
Click on each example to see the breakdown:
Example 1: Moles in 50 mL of Water
Scenario: Find the amount (moles) in 50.0 mL of pure water.
Inputs:
- Volume (V): 50.0 mL
- Density (ρ) of Water: approx. 1.00 g/mL (at 4°C, standard conditions)
- Molar Mass (MM) of Water (H₂O): approx. 18.015 g/mol (1.008*2 + 15.999)
Steps:
- Calculate Mass: Mass = $\rho \times V = 1.00 \text{ g/mL} \times 50.0 \text{ mL} = 50.0 \text{ g}$
- Calculate Moles: Moles = Mass / MM = $50.0 \text{ g} / 18.015 \text{ g/mol} \approx 2.775 \text{ mol}$
Result: Approximately 2.78 moles of water.
Example 2: Moles in 100 mL of Ethanol
Scenario: Find the amount (moles) in 100 mL of pure ethanol (C₂H₅OH).
Inputs:
- Volume (V): 100 mL
- Density (ρ) of Ethanol: approx. 0.789 g/mL
- Molar Mass (MM) of Ethanol (C₂H₅OH): approx. 46.07 g/mol (12.011*2 + 1.008*6 + 15.999)
Steps:
- Calculate Mass: Mass = $\rho \times V = 0.789 \text{ g/mL} \times 100 \text{ mL} = 78.9 \text{ g}$
- Calculate Moles: Moles = Mass / MM = $78.9 \text{ g} / 46.07 \text{ g/mol} \approx 1.713 \text{ mol}$
Result: Approximately 1.71 moles of ethanol.
Example 3: Moles in 5 mL of Mercury
Scenario: Find the amount (moles) in 5.0 mL of Mercury (Hg).
Inputs:
- Volume (V): 5.0 mL
- Density (ρ) of Mercury: approx. 13.59 g/mL
- Molar Mass (MM) of Mercury (Hg): approx. 200.59 g/mol (from periodic table)
Steps:
- Calculate Mass: Mass = $\rho \times V = 13.59 \text{ g/mL} \times 5.0 \text{ mL} = 67.95 \text{ g}$
- Calculate Moles: Moles = Mass / MM = $67.95 \text{ g} / 200.59 \text{ g/mol} \approx 0.339 \text{ mol}$
Result: Approximately 0.34 moles of Mercury.
Example 4: Moles in 10 cm³ of Iron
Scenario: Find the amount (moles) in a 10.0 cm³ block of pure Iron (Fe). Note: 1 cm³ = 1 mL.
Inputs:
- Volume (V): 10.0 mL
- Density (ρ) of Iron: approx. 7.87 g/mL (or g/cm³)
- Molar Mass (MM) of Iron (Fe): approx. 55.845 g/mol
Steps:
- Calculate Mass: Mass = $\rho \times V = 7.87 \text{ g/mL} \times 10.0 \text{ mL} = 78.7 \text{ g}$
- Calculate Moles: Moles = Mass / MM = $78.7 \text{ g} / 55.845 \text{ g/mol} \approx 1.409 \text{ mol}$
Result: Approximately 1.41 moles of Iron.
Example 5: Moles in 25 mL of Benzene
Scenario: Find moles in 25 mL of Benzene (C₆H₆).
Inputs:
- Volume (V): 25 mL
- Density (ρ) of Benzene: approx. 0.876 g/mL
- Molar Mass (MM) of Benzene (C₆H₆): approx. 78.11 g/mol (12.011*6 + 1.008*6)
Steps:
- Calculate Mass: $0.876 \times 25 = 21.9 \text{ g}$
- Calculate Moles: $21.9 / 78.11 \approx 0.280 \text{ mol}$
Result: Approximately 0.28 moles of Benzene.
Example 6: Moles in 10 mL of 98% Sulfuric Acid
Scenario: Find moles of H₂SO₄ in 10 mL of concentrated (98% w/w) sulfuric acid.
Inputs (approximate values):
- Volume (V): 10 mL
- Density (ρ) of 98% H₂SO₄: ≈ 1.84 g/mL
- Molar Mass (MM) of H₂SO₄: ≈ 98.07 g/mol
- (Note: We assume the density applies to the solution, but calculate moles of *pure* H₂SO₄ within it)
Steps:
- Calculate Mass of Solution: $1.84 \text{ g/mL} \times 10 \text{ mL} = 18.4 \text{ g}$
- Calculate Mass of Pure H₂SO₄: $18.4 \text{ g solution} \times 0.98 \text{ (g H₂SO₄ / g solution)} = 18.032 \text{ g H₂SO₄}$
- Calculate Moles of H₂SO₄: $18.032 \text{ g} / 98.07 \text{ g/mol} \approx 0.184 \text{ mol}$
Result: Approximately 0.18 moles of H₂SO₄. (This shows how density of solutions can be used, but requires care with purity).
Example 7: Moles in 2 mL NaCl crystal
Scenario: Find moles in a 2.0 cm³ (2.0 mL) crystal of Sodium Chloride (NaCl).
Inputs:
- Volume (V): 2.0 mL
- Density (ρ) of NaCl (solid): ≈ 2.16 g/mL
- Molar Mass (MM) of NaCl: ≈ 58.44 g/mol (22.990 + 35.45)
Steps:
- Calculate Mass: $2.16 \times 2.0 = 4.32 \text{ g}$
- Calculate Moles: $4.32 / 58.44 \approx 0.0739 \text{ mol}$
Result: Approximately 0.074 moles of NaCl.
Example 8: Moles in 100 mL Acetic Acid
Scenario: Find moles in 100 mL of glacial (pure) Acetic Acid (CH₃COOH).
Inputs:
- Volume (V): 100 mL
- Density (ρ): ≈ 1.05 g/mL
- Molar Mass (MM): ≈ 60.05 g/mol (12.011*2 + 1.008*4 + 15.999*2)
Steps:
- Calculate Mass: $1.05 \times 100 = 105 \text{ g}$
- Calculate Moles: $105 / 60.05 \approx 1.749 \text{ mol}$
Result: Approximately 1.75 moles of Acetic Acid.
Example 9: Moles in 1 mL of Gold
Scenario: Find moles in 1.0 cm³ (1.0 mL) of pure Gold (Au).
Inputs:
- Volume (V): 1.0 mL
- Density (ρ): ≈ 19.3 g/mL
- Molar Mass (MM): ≈ 196.97 g/mol
Steps:
- Calculate Mass: $19.3 \times 1.0 = 19.3 \text{ g}$
- Calculate Moles: $19.3 / 196.97 \approx 0.098 \text{ mol}$
Result: Approximately 0.098 moles of Gold.
Example 10: Finding Volume from Moles (Reverse Thinking)
Scenario: How many mL of Glycerol (C₃H₈O₃) corresponds to 0.5 moles?
Given/Needed Inputs for *this* calculator (to work backwards mentally or use formulas):
- Moles (n): 0.5 mol
- Density (ρ) of Glycerol: ≈ 1.26 g/mL
- Molar Mass (MM) of Glycerol: ≈ 92.09 g/mol
Steps (Reverse):
- Calculate Mass from Moles: Mass = Moles * MM = $0.5 \text{ mol} \times 92.09 \text{ g/mol} = 46.045 \text{ g}$
- Calculate Volume from Mass: Volume = Mass / Density = $46.045 \text{ g} / 1.26 \text{ g/mL} \approx 36.54 \text{ mL}$
Result: 0.5 moles of Glycerol is approximately 36.5 mL. (You could verify by plugging 36.54 mL, 1.26 g/mL, and 92.09 g/mol into the calculator above).
Frequently Asked Questions (FAQs)
Why do I need density and molar mass for this conversion?
Volume (mL) measures space, while moles measure the amount of substance. To connect them for a pure substance, you first need density (g/mL) to find the mass in that volume (Mass = Density x Volume). Then, you need molar mass (g/mol) to convert that mass into the amount of substance (Moles = Mass / Molar Mass).
Where do I find density values?
Densities for common substances can be found in chemistry handbooks (like the CRC Handbook), online chemical databases (e.g., PubChem, Wikipedia), or material safety data sheets (MSDS/SDS). Note that density is often temperature-dependent, so use the value corresponding to your conditions if high precision is needed.
How do I find the Molar Mass?
For elements, it's the atomic weight listed on the periodic table (in g/mol). For compounds, sum the atomic weights of all atoms in the chemical formula (e.g., H₂O = (2 * Atomic Weight of H) + (1 * Atomic Weight of O)).
Does this calculator work for gases?
No. The volume of a gas depends heavily on its temperature and pressure, not just density in the same way as liquids/solids. For gases, you typically use the Ideal Gas Law (PV=nRT) or the standard molar volume (approx. 22.4 L/mol at STP) to relate volume and moles.
Can I use this for solutions or mixtures (like salt water or air)?
No. This calculator assumes a **pure substance** where the entire volume consists of the substance whose molar mass you entered. For solutions, you need the **Molarity (mol/L)** and should use the Molarity Calculator.
What units must I use?
This calculator is designed for Volume in **milliliters (mL)**, Density in **grams per milliliter (g/mL)**, and Molar Mass in **grams per mole (g/mol)**. Ensure your inputs use these units for correct results.
