Better to use ml of concentrate to be diluted to specified volume. Vol Conc(ml) = [(Molarity Needed)(Volume of Soln in Liters)(formula wt of solute)]/[(Decimal Fraction of Solute in concentrate)(Density of conc soln)]
Let's assume you need 250 ml of 0.20M HCl(aq) solution.
ml conc needed = [(0.20M)(0.250L)(36g/mol)]/[(.37)(1.14g/ml)] = 4.2 ml of concentrate needed.
However, when diluting a strong acid such as HCL(37%), 1st transfer a small quantity of water into the mixing vessel (in this case ~100ml) then slowly add the 4.2ml of concentrated HCl. Adding solvent water into 4.2ml of concentrated HCl(aq) may cause the solution to flash/splash because of rapid heating during the mixing process. Addition of conc strong acid into a small quantity of water be for dilution to final volume avoids this danger.
After mixing the 4.2ml into the 100ml of solvent water, then add the remaining solvent water up to but not to exceed the 250ml mark.
Using the dilution equation gives the same volume of concentrate. HCl(37%) is ~12M... (Molarity)(Volume)concentrate = (Molarity)(Volume)diluted soln => (12)V(ml) = (250ml)(0.20M). In this, you are determining how much of the concentrate you will need (in mls.) to dilute to desired volume. Remember A&W Root Beer... Add Acid to Water(small quantity) then dilute to needed volume.
With careful attention to volumetric accuracy, either method will give an experimental error of less than ±10%.
Explain using dilution formula how to prepare 0.2M hcl acid from 37% concentrated hcl acid
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