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“Your Safer Source for Science Supplies”Laboratory SolutionPreparationMany of the reagents used in science are in the form of solutionswhich need to be purchased or prepared. For many purposes, the exactvalue of concentration is not critical; in other cases, the concentrationof the solution and its method of preparation must be as accurate aspossible. The Flinn Laboratory Solution Preparation reference sectionis designed for both the novice and experienced solution maker. Itprovides valuable information on the basic concepts of preparing solu tions and instructions for preparing most solutions required in the highschool science laboratory. Professional quality solutions are possiblewhen high quality and fresh chemicals and solvents are used, andmeticulous procedures are followed. Many of the solutions describedLaboratory Solution Preparation Basic concepts of preparingsolutions Over 300 recipes of commonlaboratory solutions Solution preparation tipsin this section are available ready-made from Flinn Scientific to savevaluable laboratory prep time.The section is divided into several parts for your convenience. Basic concepts of preparing solutions Preparation of simple inorganic salt solutions Preparations of acid and base solutions Recipes for Biological, Histological, and Chemical solutionsBasic Concepts of Preparing SolutionsMolarityThe most common unit of solution concentration is molarity (M).The molarity of a solution is defined as the number of moles ofsolute per one liter of solution. Note that the unit of volume formolarity is liters, not milliliters or some other unit. Also notethat one liter of solution contains both the solute and the solvent.Molarity, therefore, is a ratio between moles of solute and liters ofsolution. To prepare laboratory solutions, usually a given volumeand molarity are required. To determine molarity, the formulaweight or molar mass of the solute is needed. The following exam ples illustrate the calculations for preparing solutions.If starting with a solid, use the following procedure: Determine the mass in grams of one mole of solute, the molarmass, MMs. Decide volume of solution required, in liters, V. Decide molarity of solution required, M. Calculate grams of solute (gs) required using equation 1.eq. 1. gs MMs x M x V Example: Prepare 800 mL of 2 M sodium chloride.(MMNaCl 58.45 g/mol)gNaCl 58.45 g/mol x 2 mol/L x 0.8 LgNaCl 93.52 g NaClDissolve 93.52 g of NaCl in about 400 mL of distilled water,then add more water until final volume is 800 mL.If starting with a solution or liquid reagent: When diluting more concentrated solutions, decide whatvolume (V2) and molarity (M2) the final solution should be.Volume can be expressed in liters or milliliters. Determine molarity (M1) of starting, more concentrated solu tion. Calculate volume of starting solution (V1) required using equa tion 2. Note: V1 must be in the same units as V2.eq. 2. M1V1 M2V2 Example: Prepare 100 mL of 1.0 M hydrochloric acid fromconcentrated (12.1 M) hydrochloric acid.M1V1 M2V2(12.1 M)(V1) (1.0 M)(100 mL)V1 8.26 mL conc. HClAdd 8.26 mL of concentrated HCl to about 50 mL of distilledwater, stir, then add water up to 100 mL.Percent SolutionsMass percent solutions are defined based on the grams of soluteper 100 grams of solution.Example: 20 g of sodium chloride in 100 g of solution is a 20%by mass solution.Volume percent solutions are defined as milliliters of solute per100 mL of solution.Example: 10 mL of ethyl alcohol plus 90 mL of H2O (makingapprox. 100 mL of solution) is a 10% by volumesolution.Mass-volume percent solutions are also very common. Thesesolutions are indicated by w/v% and are defined as the grams ofsolute per 100 milliliters of solution.Example: 1 g of phenolphthalein in 100 mL of 95% ethylalcohol is a 1 w/v% solution.BASIC CONCEPTS OF PREPARING SOLUTIONS continued on next page. 2011 Flinn Scientific, Inc. All Rights Reserved.
1-800-452-1261Safety Referenceflinnsci.comBasic Concepts of Preparing Solutions, continuedConversion Between Percent SolutionsCalculating Molarity from Percent SolutionsYou may wish to convert mass percent to volume percent or viceversa. If so, follow this procedure:To determine the molarity of a mass percent solution,the density of the solution is required. Use the following proce dure:A 10% by mass solution of ethyl alcohol in water contains 10g of ethyl alcohol and 90 g of water.1. The formula for determining the volume of the component(ethyl alcohol in our example) is:1. Determine the mass of solution by multiplying the volume ofthe solution by the density of the solution.mass volume x densitymass of ethyl alcoholVolume ——————————density of ethyl alcohol2. Determine concentration in percent by mass of the solute insolution. Change to the decimal equivalent.2. Determine the volume of the total solution by dividing themass of the solution by the density of the solution.3. Calculate the molar mass of the compound, MM.3. Determine the percent by volume by dividing the volume ofthe component by the volume of the solution.4. Multiply mass (step 1) by mass % (step 2) and divide bymolecular mass (step 3) to find the number of moles present inthe whole solution.Let’s solve 1, 2, and 3 above as follows:5. Divide the number of moles (step 4) by the volume in liters ofthe solution to find the molarity of the solution.1. Mass of ethyl alcohol 10 g (given)Density of ethyl alcohol 0.794 g/mL (from handbook)massVolume ———density10 gVolume of ethyl alcohol ————— 12.6 mL0.794 g/mL2. Mass of solution 100 g (given)Density of solution (10% ethyl alcohol) 0.983 g/mL(fromhandbook)100 gVolume of solution ————— 101.8 mL*0.983 g/mLExample: Determine molarity of 37.2% hydrochloric acid(density 1.19 g/mL).1. Mass of solution 1,000 mL x 1.19 g/mL 1,190 g2. Mass % 37.2 % 0.3723. Molar mass of hydrochloric acid 36.4 g/mol1,190 g x 0.3724. mass x mass %———————— ———————— 12.1 moles36.4 g/molMMHCl5. Molarity moles/liters 12.1 moles/1 liter 12.1 M3. Volume percent of solutionvolume of ethyl alcohol12.6Percent —————————— ——— 12.4%total volume of solution101.8Reverse the procedure to convert volume percent to masspercent.* The volume percent statement generally is accurate but the volume percent is notalways calculated directly from the volumes of the mixed ingredients because thefinal volume may not equal the sum of the separate volumes. In our solution (No.2 above) note that if the alcohol volume (12.6 mL) is added to the water volume(90 mL), the final volume is less than 102.6 mL.DefinitionsBuffer: A solution which tends to maintain a constant pH whenexcess acid or base is added.Concentrated: For some commonly used acids and bases, themaximum solubility (at room temperature) in an aqueous solutionor as a pure liquid.Concentration: The relative amount of solute and solvent in asolution.Hydrates: Compounds containing water chemically combined ina definite ratio. Computations using formula weight must take thewater molecules into account.Miscible: The ability of two liquids to be completely soluble inone another.Molality: A concentration unit (m); defined as the number ofmoles of solute divided by the number of kilograms of solvent.Molar Mass: The mass of a mole of any element or compound.Molarity: A concentration unit (M); defined as the number ofmoles of solute divided by liters of solution. 2011 Flinn Scientific, Inc. All Rights Reserved.
“Your Safer Source for Science Supplies”Preparation of Simple Inorganic Salt SolutionsPreparation of Simple Inorganic Salt SolutionsName / Formula / F.W.Concentrationg/LName / Formula / F.W.Concentrationg/L0.2 M63.1 g in500 mL 3MHCl*Aluminum chlorideAlCl3 6H2O241.430.2 M0.05 M48.3 g12.1 gBismuth trichlorideBiCl3315.34Aluminum nitrateAl(NO3)3 9H2O375.130.1 M37.5 gCadmium chlorideCdCl2 2 1 2H2O228.340.1 M22.8 gAluminum sulfateAl2(SO4)3 18H2O666.420.1 M66.6 gCadmium nitrateCd(NO3)2 4H2O308.490.1 M30.8 gAmmonium acetateNH4C2H3O277.081.0 M0.1 M77.1 g7.7 gCalcium acetateCa(C2H3O2)2 H2O176.190.5 M0.1 M88.1 g17.6 gAmmonium chlorideNH4Cl53.491.0 M0.5 M53.5 g26.7 gCalcium chlorideCaCl2 2H2O147.021.0 M0.1 M147.0 g14.7 g2 g†1.0 M0.5 M0.1 M80.0 g40.0 g8.0 gCalcium hydroxideCa(OH)274.10saturatedAmmonium nitrateNH4NO380.04Ammonium sulfate(NH4)2SO4132.10.1 M13.2 gCalcium nitrateCa(NO3)2 4H2O236.160.5 M0.1 M118.1 g23.6 g0.1 M26.6 gBarium chlorideBaCl2 2H2O244.280.1 M24.4 gChromium(III) chlorideCrCl3 6H2O266.480.1 M40.0 gBarium hydroxideBa(OH)2 8H2O315.500.1 M31.5 gChromium(III) nitrateCr(NO3)3 9H2O400.180.1 M23.8 gBarium nitrateBa(NO3)2261.350.5 M0.1 M130.7 g26.1 gCobalt(II) chlorideCoCl2 6H2O237.950.1 M29.1 gBismuth nitrateBi(NO3)3 5H2O485.10.1 M48.5 g in500 mL 6MHNO3*Cobalt(II) nitrateCo(NO3)2 6H2O291.05Copper(II) chlorideCuCl2 2H2O170.490.5 M0.1 M85.2 g17.0 gCopper(II) nitrateCu(NO3)2 3H2O241.60.5 M0.1 M120.8 g24.2 gSaturated Solution: A solution that contains the maxi mum amountof a particular solute that will dissolve at that temperature.Copper(II) sulfateCuSO4 5H2O249.691.0 M0.5 M249.7 g124.8 gSolute: The substance which is dissolved, or has gone into solution(typically a solid).Iron(II) sulfateFeSO4 7H2O278.030.01 M2.8 g and1 mL conc.H2SO4*Iron(III) chlorideFeCl3 6H2O270.321.0 M0.1 M270.3 g27.0 gIron(III) nitrateFe(NO3)3 9H2O404.000.1 M40.4 gNormality: A concentration unit (N); defined as the number ofequivalents of solute per liter of solution. (e.g., 1 M H2SO4 2 N H2SO4)Solution: A uniform homogeneous mixture of two or moresubstances. The individual substances may be present in varyingamounts.Solvent: The substance which does the dissolving (typically aliquid, such as water or alcohol). Must be greater than 50% of thesolution.Standard Solution: A very precise solution, usually to 3–4significant figures, used in quantitative analysis or an analyticalprocedure.Supersaturated Solution: A solution that contains more solutethan equilibrium conditions allow; it is unstable and the solute mayprecipitate upon slight agitation or addition of a single crystal.* Add solid to acid solution, stir, then add to water. Dilute to 1 L. Remember,always add acid to water.† Approximate amount for 1 L of saturated solution. Keep adding solute until itno longer dissolves; stir for 1 hour, then filter.PREPARATION OF SIMPLE INORGANIC SALT SOLUTIONScontinued on next page. 2011 Flinn Scientific, Inc. All Rights Reserved.
1-800-452-1261Safety Referenceflinnsci.comPreparation of Simple Inorganic Salt Solutions, continuedName / Formula / F.W.ConcentrationLead acetatePb(C2H3O2)2 3H2O379.340.1 Mg/LName / Formula / F.W.38.0 gManganese sulfateMnSO4 H2O169.01Concentrationg/L0.2 M0.1 M33.8 g16.9 g0.25 M0.10 M67.9 g27.2 gsaturated12.0 g†Lead nitratePb(NO3)2331.21M0.5 M0.1 M331.2 g§165.6 g33.1 gMercury(II) nitrateHg(NO3)2 H2O342.630.1 M34.2 g in50 mL conc.HNO3*Lithium carbonateLi2CO373.890.1 M7.4 gMercury(I) nitrateHg2(NO3)2 2H2O561.220.1 M56.2 g in100 mL conc.HNO3*Lithium chlorideLiCl42.401.0 M0.1 M42.4 g4.2 gMercury(I) sulfateHg2SO4497.240.1 M49.7 g in30 mL 1 MHNO3*Lithium nitrateLiNO368.951.0 M0.5 M69.0 g34.5 gNickel chlorideNiCl2 6H2O237.720.25 M0.1 M59.4 g23.8 gMagnesium bromideMgBr2 6H2O292.250.1 M29.2 gNickel nitrateNi(NO3)2 6H2O290.821M0.2 M290.8 g58.2 gMagnesium chlorideMgCl2 6H2O203.331.0 M0.1 M203.3 g20.3 gNickel sulfateNiSO4 6H2O262.871.0 M0.5 M262.9 g131.4 g300 g†Potassium bromideKBr119.020.5 M0.1 M59.5 g11.9 gPotassium carbonateK2CO3138.210.5 M0.1 M69.1 g13.8 gPotassium chlorideKCl74.560.5 M0.1 M37.3 g7.5 gLead chloridePbCl2278.12Magnesium hydroxideMg(OH)258.34saturatedMagnesium nitrateMg(NO3)2 6H2O256.430.1 M25.6 gMagnesium sulfateMgSO4 7H2O246.500.5 M0.1 M123.3 g24.7 gManganese chlorideMnCl2 4H2O197.910.5 M0.1 M99.0 g19.8 gMercury(II) chlorideHgCl2271.50* Add solid to acid solution, stir, then add to water. Dilute to 1 L. Remember,always add acid to water.† Approximate amount for 1 L of saturated solution. Keep adding solute until itno longer dissolves; stir for 1 hour, then filter.§ Use 7.5 mL conc. HNO3 to help dissolve.PREPARATION OF SIMPLE INORGANIC SALT SOLUTIONS continued on next page.Make a Solution2. Fill volu met ric flask1 3 –1 2full withdeionizedor distilledwater.3. Transfersolid, washout weigh ing dish.4. Stir untildissolved.Add morewater ifnecessary.5. Adddeionizedor distilledwater upto mark.1. Weigh solid. 2011 Flinn Scientific, Inc. All Rights Reserved.
Preparation of Simple Inorganic Salt Solutions PREPARATION OF SIMPLE INORGANIC SALT SOLUTIONS continued on next page. Name / Formula / F.W. Concentration g/L Bismuth trichloride 0.2 M 63.1 g in BiCl 3 500 mL 3M 315.34 HCl* Cadmium chloride 0.1 M 22.8 g CdCl 2 • 21? 2H 2O 228.34 Cadmium nitrate 0.1 M 30.8 g Cd(NO 3) 2 • 4H 2O 308.49
“Your Safer Source for Science Supplies”Preparation of Simple Inorganic Salt SolutionsPreparation of Simple Inorganic Salt Solutions, continuedName / Formula / F.W.Concentrationg/LPotassium chromateK2CrO4194.211.0 M0.5 M0.1 M194.2 g97.1 g19.4 gPotassium dichromateK2Cr2O7294.220.1 M29.4 gPotassium ferricyanideK3Fe(CN)6329.260.5 M0.1 M164.6 g32.9 gPotassium ferrocyanideK4Fe(CN)6 3H2O422.410.1 MPotassium hydrogenphthalateKHC8H4O4204.230.1 MConcentrationg/LPotassium phosphate,tribasicK3PO4212.270.1 M21.2 gPotassium sulfateK2SO4174.270.5 M0.1 M87.1 g17.4 g42.2 gPotassium thiocyanateKSCN97.181.0 M0.5 M0.1 M97.2 g48.6 g9.7 g20.4 gSilver nitrateAgNO3169.870.5 M0.1 M84.9 g17.0 gSodium acetateNaC2H3O2 3H2O136.081M0.5 M136.1 g68.0 gSodium bicarbonateNaHCO384.010.5 M0.1 M42.0 g8.4 gSodium borateNa2B4O7 10H2O381.424%40.0 g1.0 M0.1 M102.9 g10.3 gPotassium hydroxide see page 118Name / Formula / F.W.Potassium iodateKIO3214.01saturated0.2 M0.1 M214.0 g†42.8 g21.4 gPotassium iodideKl166.011M0.5 M0.2 M166.0 g83.0 g33.2 gPotassium nitrateKNO3101.110.5 M0.1 M50.6 g10.1 gSodium bromideNaBr102.900.2 M0.1 M0.01 M31.6 g15.8 g1.6 gSodium carbonateNa2CO3105.99Potassium phosphate,monobasicKH2PO4136.090.1 M13.6 gSodium carbonateNa2CO3 H2O124.00Potassium phosphate,dibasicK2HPO4174.180.1 M17.4 gPotassium permanganateKMnO4158.04saturated1.0 M0.1 M1.0 M0.1 M214.0 g†106.0 g10.6 g124.0 g12.4 g* Add solid to acid solution, stir, then add to water. Dilute to 1 L. Rem