Engineering
Molarity (M) & lab solution bench-prep mass formula (Grams = M × L × MW)
Convert mass, molar mass and final solution volume to molarity, and calculate theoretical solute mass for a target concentration.
Forward Molarity (mol/L) and reverse bench-scale solute mass (Grams)
Using a molar mass of 58.44 g/mol,29.22 g of the assumed pure solute in a final solution volume of 500 mL gives 1 mol/L. Final solution volume is not the amount of solvent initially added.
A target of 0.15 mol/L in 500 mL gives a theoretical mass of 4.383 g under those assumptions. This is a numerical chemistry exercise, not preparation instructions for medical saline or a sterile product.
Use the molar mass for the actual chemical form, including hydration where applicable. The calculation assumes complete dissolution and the stated purity; it does not adjust for purity, reactions, temperature-dependent volume or activity. Follow a substance-specific validated procedure for physical preparation.
| Stoichiometry Calculation (NaCl MW = 58.44 g/mol) | Formula | Result |
|---|---|---|
| Moles of Solute (29.22 g / 58.44) | =A2 / B2 | 0.5000 mol |
| Solution Molarity (29.22 g in 500 mL) | =(A2 / B2) / (C2 / 1000) | 1.0000 M (mol/L) |
| Grams Needed for 500 mL of 0.15 M solution | =D2 * (C2 / 1000) * B2 | 4.3830 g NaCl |
Molarity (mol/L) from solute grams, Molecular Weight, and volume in mL
Dividing C2 / 1000 converts volumetric flask sizes (100 mL, 250 mL, 500 mL) directly into Liters.
=IF(OR(COUNT(A2:D2)<>4,A2<0,B2<=0,C2<=0,D2<0),"Invalid solution inputs",ROUND((A2 / B2) / (C2 / 1000), 4))Grams of dry reagent to weigh for Target Molarity D2 in C2 mL
Calculates theoretical mass only. It does not specify a universal mixing procedure.
=IF(OR(COUNT(A2:D2)<>4,A2<0,B2<=0,C2<=0,D2<0),"Invalid solution inputs",ROUND(D2 * (C2 / 1000) * B2, 4))Try the example
Use the original values or change them to test your understanding.