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Weighing and preparation of solution of different strength and their dilutions.pptx

chemistry topic, veterinary PGS P.G. Coursework

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Weighing and preparation of solution of different strength and their dilutions Submitted by – Dr. Akshit Tyagi V-15076/23 PG Scholar Department of Vet. Pathology A.N.D.U.A.T., Kumarganj, Ayodhya
we will discuss… ●Solutions ●Measuring chemicals ●Different chemicals concentrations ●Dilutions of stock solutions
Solutions ● Solution uniform homogenous mixture of two or more substances i.e, solute and solvent. Solution=solute+solvent ● Solute- A Solute is a substance that can be dissolved into a solvent. ● Solvent- A solvent is a substance in which a substance dissolve.
continue…. ● Standard solution very precise solution,usually 3-4 significant figures,used in quantitative analysis or an analytic procedure. ● Saturated solution a solution that contain the maximum amount of a particular solute that will dissolved at the temperature. ● Supersaturated solution a solute that contains more solute than equilibrium condition allow;it is unstable and the solute may precipitate upon slight agitation or addition of single crystal.
Preparing Solutions Solutions of known concentration can be prepared in a number of different ways depending on the nature of the analyte and/or the concentration required: ● Weighing out of solid material of known purity,dissolving it in a suitable solvent and diluting to the required volume. ● Weighing out a liquid of normal purity,dissolving it in a suitable solvent and diluting to the required volume. ● Diluting a solution previously prepared in the laboratory. ● Diluting a solution from a chemical supplier.
Weight measurements Basic protocol 1; measuring mass using a top loading balance 1. Turn on balance and wait for display to read 0.0 g. 2. place weighing vessel on the balance pan (e.g.,creased weighing paper,weight boat. 3. press tare button so that display reads 0.0g. 4. gently add the substance being weighed to the weighing sample. 5. record mass. 6. remove weighed sample. 7. clean spills off balance with brush or absorbant laboratory tissue. 8. discard any disposal weighing vessel.
contd… Basic protocol 2: Measuring mass using an analytical balance 1. Turn on balance and wait for display to read 0.000g. 2. Check the level indicator & do not lean on table while weighing. 3. Place weighing vessel on the balance pan(e.g., creased weighing paper,weigh boat) 4. Close the sliding doors & wait for stability light indicator,indicating that the weight is stable. 5. Press tare button so that display reads 0.0g. 6. gently add the substance being weighed to the weighing sample. 7. Record mass. 8. Remove weighed sample. 9. Clean spills off balance with bruss or absorbent laboratory tissue.disacard any disposal weighing vessel.
Volume measurments Volumetric or transfer pipettes Micropipettes
Volumetric Containers
1.Molar solution ● molarity is number of moles of a solute that are dissolved per liter of total solution. ● A 1 M Solutions contains 1 mole of solute per liter total volume. ● Example: A 1M solution of H2SO4 contains 98.06 g of sulfuric acid in liter of total solution. “mole” is an expression of amount “molarity” is an expression of concentration.
contd… ● Example- How much amount of KOH is required to prepare 0.1M KOH solution in 100 ml of distilled water. ○ Molarity(M) = 0.1M ○ weight of KOH=X ○ molecular weight of KOH= 56 ○ volume taken= 100 ml ○ Molarity(M)=weight of KOH/molecular weight of KOH× 1000ml/total volume taken ○ 0.1M=X/56×1000ml/100 ○ 5.6=10X ○ X=0.56g
2. Normal solutions ● Normality is defined as the gram Eq.wt. of the solute per L of the solvent. 1N sol. = EW solute/1L of sol. ● Conc. of acids and alkalis are usually expressed in this unit. ● gram Eq.wt. is M.W divided by the no. of H+ or OH- ions released from 1 molecules of the acids or base,respectively in solutions. Eq.wt. = Molecular Weight of the substnace /replaceble no. of H+ or OH-
cont…. Example - Calculate the normality of NaOH,When 2g is present in 800 ml solution. weight of NaOH =2g Molecular weight of NaOH=40g volume taken=800ml Normality=Molarity×n factor Normality=[weight of NaOH/molecular weight of NaOH×1000/volume taken] n factor n factor = 1 Normality=[2/40×1000/800]1 Normality=[0.0625]1 N=0.0625
3.Molal solutions ● Molality expresses the no. of moles per 1000g or 1 kg of solvent. ● It is dependent on the density of solvent. ● It is different from molarity as the later refers to volume of the solution,which is temperature dependent. ● Molal solution are not ususaly used in biochemical experiments.
4. Percent solution ● Mass percent solutions are defined based on the grams of solute per 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 ml of solute per 100 mL of solution. Example: 10 mL of ethyl alcohol + 90 ml of H2O (making approx. 100 mL of solution) is a 10% by volume solution. ● Mass-volume percent solutions are also very common. These solutions are indicated by w/v % & are defined as the grams of solute per 100 mL of solution. Example: 1 g of phenolphthalein in 100 mL of 95% ethyl alcohol is a 1 w/v
5. PPM and PPB ● PPM: The number of parts of solute per 1 million parts of total solution. ● ppb: The number of parts of solute per billion parts of solution. Example 5 ppm chlorine =5 g of chlorine in 1 million g of solution. or 5 mg chlorine in 1 million mg of solution. or 5 pounds of chlorine in 1 million pounds of solution
To Assure the quality of a solution ● Know the solutions & diferent conc. to represent them. ● Documentation,labeling & recording what was done. ● Treceability. ● Taintenance and calibration of instruments. ● Stability and expiry date record. ● Proper storage.
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