MAC

Chemistry

Molarity and Concentration Calculator

Calculate purity-adjusted solute mass, moles, stock molarity, mass concentration, aliquot moles, and diluted molarity from laboratory preparation inputs.

Solute mass (g)Molar mass (g/mol)Solution volume (mL)Aliquot volume (mL)Aliquot diluted volume (mL)Solute purity (%)Entered molarity comparison

Purity-adjusted solute mass-

Moles of solute-

Solution volume (L)-

Stock molarity-

Moles in aliquot-

Diluted volume (L)-

Diluted aliquot molarity-

Stock mass concentration-

Stock molarity minus comparison-

Decision view

Mass, moles, stock, and dilution pathway

Mass, moles, stock, and dilution pathwayPurity-adjusted mass becomes moles, stock molarity, conserved aliquot moles, and diluted molarity in sequence.

Exact scenario comparisonSolute purity (%) changes while all other entered assumptions remain constant.

Solute purity (%)	Purity-adjusted solute mass	Moles of solute	Solution volume (L)	Stock molarity	Moles in aliquot	Diluted volume (L)	Diluted aliquot molarity	Stock mass concentration	Stock molarity minus comparison

How to use Molarity and Concentration Calculator

Enter material mass, purity, and molar mass.
Enter the prepared stock volume.
Enter the aliquot and its final diluted volume.
Follow the live mass-to-moles-to-concentration path.

Calculator guide

Understanding Molarity and Concentration Calculator

Preparing and diluting a solution requires three distinct conversions: purity-adjusted mass to moles, millilitres to litres, and transferred aliquot moles to a new final volume. Keeping those stages visible prevents millilitre and litre factors from being applied in the wrong place.

Purity first Only adjusted mass becomes solute moles.

Litres matter Every molarity denominator is converted to litres.

Moles are conserved Dilution changes volume, not aliquot moles.

Chain is auditable Each conversion appears separately.

Calculation method

How the calculation works

Adjust entered mass for purity, convert it to moles, normalize by solution volume, and carry an exact aliquot into a second dilution calculation. The aliquot branch conserves moles and converts millilitres to litres exactly once. Apply the purity fraction to mass, divide by molar mass, convert solution volumes to litres, calculate stock molarity, then conserve aliquot moles through dilution.

Detailed calculation process

Trace mass through moles, stock concentration, and aliquot dilution

The default preparation uses 14.61 g of 99.5% material with molar mass 58.44 g/mol in 500 mL, then dilutes a 25 mL aliquot to 250 mL.

General formula: m_p = m(P/100)n = m_p/M_rV_s = V_s,mL/1000C_s = n/V_sn_a = C_s(V_a,mL/1000)C_d = n_a/(V_d,mL/1000) Purity determines the actual solute mass. Molar mass converts that mass to amount of substance, litres normalize the stock concentration, and the aliquot carries a proportional share of stock moles into the diluted volume.

What each symbol means

m, m_p Entered material mass and purity-adjusted solute mass (g).

P Entered solute purity (%).

M_r Molar mass (g/mol).

n, n_a Total solute moles and moles transferred in the aliquot (mol).

V_s, V_a, V_d Stock, aliquot, and diluted volumes (L after conversion).

C_s, C_d Stock and diluted molarity (mol/L).

Worked substitution with the default inputs

1. Adjust the entered mass for purity P = 99.5/100 = 0.995m_p = 14.61(0.995) = 14.53695 g Only the purity-adjusted portion is treated as the named solute.

2. Convert mass to moles n = 14.53695 g/(58.44 g/mol) = 0.24875 mol Grams cancel, leaving moles.

3. Calculate stock molarity V_s = 500 mL/1000 = 0.500 LC_s = 0.24875/0.500 = 0.4975 mol/L Molarity requires litres, not millilitres.

4. Transfer aliquot moles and dilute n_a = 0.4975(25/1000) = 0.0124375 molC_d = 0.0124375/(250/1000) = 0.04975 mol/L The same aliquot moles are spread through ten times the aliquot volume.

5. Reconcile concentration and mass C_s V_s = 0.4975(0.500) = 0.24875 molm_p/V_s = 14.53695/0.500 = 29.0739 g/L The stock concentration reproduces total moles, and the independent mass-concentration result preserves the same adjusted mass.

The defaults produce 0.24875 mol, a 0.4975 M stock, and a 0.04975 M diluted aliquot.

Concentration pathway

Follow solute quantity through preparation and dilution

A mass-to-moles-to-stock-to-aliquot pathway keeps the conserved quantity and both concentration stages visible.

Adjusted mass Entered mass after purity.

Moles Chemical amount from molar mass.

Stock Moles normalized by stock litres.

Dilution Aliquot moles divided by final litres.

Worked situations

Practical examples

Fourteen-point-six-one grams at 99.5% contains 14.53695 g of solute.
The 500 mL stock is 0.4975 M.
Diluting 25 mL to 250 mL reduces molarity by a factor of ten.

Better inputs

Useful tips

Verify whether the molar mass includes waters of hydration.
Use calibrated final solution volume rather than solvent volume alone.
Keep all aliquot and dilution glassware units explicit.

Before relying on the result

Limitations and common mistakes

The calculation excludes activity coefficients, reactions, volume nonadditivity, and temperature effects.
Purity and molar mass must describe the same chemical form.
Laboratory hazards and preparation procedures require appropriate professional controls.

Reference

Key terms

Molarity: Moles of solute per litre of final solution.
Aliquot: A measured portion removed from the stock solution.
Purity: Mass fraction of the entered material treated as the target solute.
Mass concentration: Purity-adjusted solute grams per litre.

Important note

Calculated from the entered values using the displayed chemical relationship. Confirm identity, units, purity, conditions, and laboratory safety requirements.

Frequently asked questions

Why divide millilitres by 1,000?

Molarity is defined per litre.

Does dilution change aliquot moles?

Not in this conserved-solute model.

Why adjust mass for purity?

The balance mass can include material other than the target solute.

Is 0.5 M the default result?

No. The purity adjustment makes the stock 0.4975 M.