Reagent Preparation Calculator

Preparing a solution of a specific molar concentration starts from the basic relationship that moles of solute equal molarity multiplied by volume in liters, and mass equals moles multiplied by the solute's molecular weight -- so this calculator converts your desired molarity and volume into the moles needed, then multiplies by molecular weight to get the mass in grams. That "grams needed" figure assumes a perfectly pure reagent, which real reagent bottles rarely are: a bottle labeled 98% purity means only 98% of its mass is the actual compound, with the remainder typically water of hydration, residual solvent, or manufacturing byproducts. The calculator divides the pure-reagent mass by the purity fraction to report the actual mass you need to weigh out from that specific bottle -- using the pure-reagent figure with an impure reagent would under-dose the solution and produce a molarity lower than intended. Always read the purity percentage or assay value from the reagent's certificate of analysis or bottle label rather than assuming 100%, since even reagent-grade chemicals commonly ship at 95-99.9% purity rather than exactly 100%.

This calculator handles simple aqueous dissolution of a solid reagent into a target volume, following real quantum sufficit (q.s.) lab practice: the FINAL solution volume equals your target Desired Volume, and Volume of Solvent is that target volume minus the volume the dissolved solute itself displaces, not a separate quantity added on top of the target. Because this calculator doesn't collect the solute's actual density, the displaced volume is estimated from a generic solid-reagent density -- an approximation layered on top of the fact that it also does not account for volume contraction on dissolution (the true mixed volume of a solute and solvent is not always the simple sum of their individual volumes), or for preparing a dilution from an existing concentrated stock solution, which uses a different calculation (C1V1 = C2V2). Treat Volume of Solvent as a practical starting estimate, not a substitute for actually dissolving to a calibrated volumetric mark.