SOLUTIONS-2 SOLUTION CONCENTRATIONS
SOLUTION CONCENTRATIONS •There are a number of ways one can measure concentration of solute in solutions •Molarity –commonly used since volumes of solutions are easy to measure •Mole fraction –used for gases and vapor pressures of solutions •Molality –temperature independent
Introduction to Solution Chemistry Concentrations of Solutions
Mar 25, 2016 · the concentrations of very dilute solutions This is useful when very little solute is dissolved in a very large volume of water; for example the amount of dissolved oxygen in a lake Parts per Million of Solute = (Mass of Solute/ Mass of solution ) * 10 6 ppm = (mass solute/ mass solution) X 1,000,000 Parts per Million {PPM} I 32 3/25/2016
122 Concentration of Solutions - chemrevise
Dec 01, 2019 · both solutions have halved Questions 3 1) If 5 0g of Sodium chloride is added to 250 cm3 of a solution of 0 10 mol dm-3 HCl, what will be the concentrations of NaCl and HCl after they are added together?
Concentrations and Dilutions - Savvas
solutions INTRODUCTION Concentrations of many pharmaceutical preparations are expressed as a percent strength This is an important concept to understand Percent
Honors Chemistry Name
Concentrations of Solutions Date _____ Complete the following problems on a separate sheet of paper Use significant figures Note: The density of water is 1 g/mL 1 What is the molarity of a solution that contains 10 0 grams of Silver Nitrate that has been dissolved in 750 mL of water? 10 0"" 1 1"#$""
Lab Math Solutions, Dilutions, Concentrations and Molarity
Solutions & Dilutions Preparing solutions and making dilutions Simple dilutions Mixing parts or volumes Serial dilutions Making fixed volumes of specific concentrations from liquid reagents: (C1)(V1)=(C2)(V2) Percent solutions (= parts per hundred) Molar solutions (unit=M=moles/L)
ScE732 : Solutions and Concentrations - ANSWERS
ScE7 3 2 – Solutions – 2019 – p 9 Solubility : Saturated and Unsaturated Solutions So, salt is soluble in water, but is there a limit? Yes You can only dissolve so much and then if you keep adding more salt it just sits in the bottom Explain the difference between a saturated and an unsaturated solution
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Concentration =amountvolumeUnit of concentration: mol dm-3or MUnit of Volume:dm3
A solution is a mixture formed when a solute dissolves in a solvent. In chemistry we most commonly usewater as the solvent to form aqueous solutions. The solute can be a solid, liquid or a gas.Molar concentration can be measured for solutions. This is calculated by dividing the amountin moles of the solute by the volume of the solution. The volume is measure is dm3. The unitof molar concentration is mol dm-3; it can also be called molar using symbol M
Mass ConcentrationThe concentration of a solution can also bemeasured in terms of mass of solute per volumeof solutionMass Concentration =massvolumeUnit of mass concentration: g dm-3Unit of MassgUnit of Volume:dm3Ions dissociatingWhen soluble ionic solids dissolve in water they will dissociate into separate ions. This can lead to theconcentration of ions differing from the concentration of the solute.If 5.86g (0.1 mol) of sodium chloride (NaCl) is dissolved in 1dm3of water then the concentration of sodiumchloridesolutionwould be0.1mol dm-3.However the 0.1mol sodium chloride would split uptoform 0.1mol of sodium ions and0.1mol of chloride ions. Theconcentration of sodium ions is therefore 0.1 mol dm-3and theconcentration of chloride ions is also 0.1 mol dm-3NaCl(s) +aqNa+(aq)+ Cl-(aq)0.1mol0.1mol0.1molIf 9.53g (0.1 mol) of magnesium chloride (MgCl2) is dissolvedin 1 dm3of water then the concentration of magnesium chloridesolution (MgCl2aq) would be0.1mol dm-3.However the 0.1mol magnesium chloride would split upto form0.1 mol of magnesium ions and 0.2 mol of chloride ions. Theconcentration of magnesium ions is therefore 0.1 mol dm-3andthe concentration of chloride ions is now 0.2 mol dm-3MgCl2(s) +aqMg2+(aq)+ 2Cl-(aq)0.1mol0.1mol0.2molQuestions1.1) If25.0 gof potassium nitrate (KNO3) was dissolved in 750cm3of water, what would be the molarconcentration?1.2) Calculatethe concentrationin mol dm-3of 3.78 g of potassium iodide (KI) in 35 cm3of solution1.3) Calculatethe concentrationin mol dm-3of 5.10 kg of sodium bromide in 0.250 m3of solution1.4)What mass of Na2CO3would be needed to make 500cm3of 0.250moldm-3solution?1.5) If 8.20 g of CaCl2was dissolved in 50cm3of water, what would be the concentration of chloride ions inmol dm-3?1.6) a)Calculate the mass of Borax Crystals Na2B4O7.10H2O needed to make up 250cm3of 0.100 mol dm-3solutionb)Calculate themass concentration of this solution be in g dm-31.7)Calculate themass of hydrated magnesium chloride (MgCl2.6H2O)neededto make up 500 cm3of asolution of 0.100 mol dm-3of chloride ions1.8) For drivers in the UK, the legal limit of the concentration of ethanol (molar mass 46.0 g mol-1) in theblood is 80.0 mg per 100 cm3. What is this equivalent to in concentration measured in mol dm-3?1.9) How many moles ofionsare present in 30 cm3of 0.050moldm-3calcium chloridesolution, CaCl2(aq)1.10) The concentration of blood glucose can be given inmillimolesper dm3ormmoldm-3. 5.0mmoldm-3is a normal value of the concentration. Glucose has a molar mass of 180 gmol-1. What mass of glucosedissolved in 1 dm3of blood wouldgive this normal reading?1.11) A saturated aqueous solution of magnesium hydroxide contains 1.17 mg of Mg(OH)2in 100 cm3ofsolution. Assume the magnesium hydroxide is fully dissociated into ions.Calculate theconcentration ofmagnesium ions inmoldm-3
Shake the volumetric flask thoroughlyto ensure a uniform concentrationWeigh the sample bottle containing the required mass ofsolid on a 2dpbalanceTransfer toa beakerand reweigh sample bottleRecord the difference in massAdd100 cm3of distilled water to the beaker. Use a glassrod to stir to help dissolve the solid.Sometimes the substance may not dissolve well in coldwater so the beaker and its contents could be heated gentlyuntil all the solid had dissolved.Pour solution into a250 cm3graduated flask via a funnel.Rinse beaker and funnel and add washings from thebeaker and glass rod to the volumetric flask.make up to the mark with distilled water using a droppingpipette for last few drops.Invert flask several times to ensure uniform solution.
Making a solution
Alternatively the known mass ofsolid in the weighing bottle could betransferredto beaker,washed andwashings added to the beaker.
Remember to fill so the bottom of themeniscus sits on the line on the neck ofthe flask. With dark liquids like potassiummanganateit can be difficult to see themeniscus.
Graduated/volumetric flask
A graduated flask has one mark on the neck which thelevel to fill to get the accurate volume. Do not heat or puthot solutions in the volumetric flask because the heatwould cause the flask to expand and the volume wouldthen be incorrect.
Use a teat pipette to make up to the markin volumetric flask to ensure volume ofsolution accurately measured and onedoesn"t go over the lineDiluting a solutionPipette 25cm3of original solution into volumetric flaskmake up to the mark with distilled water using adropping pipette for last few drops.Invert flask several times to ensure uniform solution.Using a volumetric pipette is moreaccurate than a measuring cylinderbecause it has a smaller sensitivity errorDilutions
Calculating DilutionsDiluting a solution will not change the amount of moles of solute present but increase the volume ofsolution and hence the concentration will lowerAmount = volume X concentrationIf amount of moles does not change thenOriginal volume x original concentration = new diluted volume x new diluted concentrationnew diluted concentration = original concentration xoriginalvolumenew diluted volumesoThe new diluted volume will be equal to the original volume of solution added + the volume ofwater added.Example50cm3of water are added to 150 cm3of a 0.20 mol dm-3NaOHsolution. Calculatethe concentration of thedilutedsolution.newdiluted concentration = original concentration xoriginalvolumenew diluted volumenew diluted concentration = 0.20 x0.1500.200= 0.15 mol dm-3Questions2.1) If 90.0cm3of water are added to 50.0 cm3of a 1.00 mol dm-3HNO3solution, what will theconcentration of the diluted solution be?2.2) How much water would need to be added to 100 cm3of a 0.15 mol dm-3NaOHsolution to dilute itto a concentration of 0.05 mol dm-3?2.3) What volume of 0.1 mol dm-3NaCl solution can be made by adding water to dilute 50 cm3of 10mol dm-3NaCl?2.4) How much water would need to be added todilute 25.0 cm3of a 12.0mol dm-3HClsolution tomake a 0.500mol dm-3HClsolution?2.5) A student is provided with a 5.00 cm3sample of 1.00×10-2moldm-3hydrochloric acid. Thestudent is asked to prepare a hydrochloric acid solution with a concentration of 5.00×10-4moldm-3bydiluting the sample with water. How much water should they add?
Concentrations of mixturesAdding a solid to a solutionIf a second solid solute is added to an existing solution of a different solute then the new mixture will have aconcentration for both solutes. If the two solutes do not react with each other then there will be no change inthe amount of moles of either solute.0.3 mol ofsolid NaCl0.5 mol of KCl dissolved in100cm3of water:concentration 0.05 moldm-3
Add thesolid NaClto the KClsolutionNow have 0.3 mol of NaCl and 0.5 molof KCl dissolved in 100cm3of waterIn the mixture the concentration of NaCl is0.03 moldm-3and the concentration of KCl is0.05 moldm-3. Note the concentration of KClhas not changedAdding two different solutions togetherIf a second solution is added to an existing solution of a different solute then the new mixture will have aconcentration for both solutes. If the two solutions do not react with each other then there will be no change inthe amount of moles of either solute.Add thesolution ofNaCl to the KClsolution0.4 mol of NaCldissolved in 100cm3of water:concentration 0.04moldm-30.5 mol of KCldissolved in 100cm3of water:concentration 0.05moldm-3Now have 0.4 mol of NaCl and 0.5 molof KCl dissolved in 200cm3of waterIn the mixture the concentration of NaCl is0.02 moldm-3and the concentration of KClis 0.025 moldm-3. Note the concentration ofboth solutions have halvedQuestions3.1) If 5.0g of Sodium chloride is added to250 cm3of a solution of0.10moldm-3HCl, what will be theconcentrations of NaCl and HCl after they are added together?3.2) If 50cm3of 0.10mol dm-3potassium chloride solution is added to 150cm3of 0.15 mol dm-3HCl, what will bethe concentrations of KCl and HCl after they are added together?3.3) A student has a 0.10 mol dm-3solution of NaCl and a 0.20 mol dm-3solution of KCl. The student wants tomake a mixture of the two solutions where the NaCl has a concentration of 0.075 mol dm-3and the KCl has aconcentration of 0.050 mol dm-3when mixed together. What ratio of volume of NaCl to volume of KCl wouldmake the new concentrations?
Density
density=massvolumeDensity is usually given in g cm-3Care needs to be taken if different units areused.Example: How many molecules of ethanol are there in a 0.500 dm3of ethanol(CH3CH2OH) liquid ? The density of ethanol is 0.789 g cm-3
Number ofmolecules =amount x 6.02 x 1023=8.576 x 6.02 x 1023= 5.16x1024(to3 sig fig) Mass= density xvolume= 0.789 x 500= 394.5gethanolamount= mass/Mr= 394.5/ 46.0= 8.576 molDensity is used in chemistry for pure substances rather than mixtures. Most commonly we would use it workout the mass of an known volume of a pure organic liquid such as ethanol, and then we would often convertthe mass into amount in moles.
4.5) A fighter plane holds 0.2230 m3of hydrazine (N2H4) and 0.860 m3of methanol (CH3OH)in its fuel tank. Density of N2H4= 1.021 g cm-3Density of CH3OH = 0.7918 g cm-3a)What is the total mass of the two substances?b) What is the total number of molecules in the fueltank?4.6 ) Concentrated hydrochloric acid is sold as a 38% by mass solution with a density of1.2 g cm-3. Calculate the concentration of this solution inmoldm-34.7) Given that the density of pure water is 1.0 kgdm-3, calculate the concentration ofpure water in moldm-3.
4.4)The density of calcium is 1.55 gcm-3Calculateits molarvolume,i.e. the volume (in m3) occupied by 1 mol.
Questions4.1) A chemist needed to add 0.100mol of ethanol (CH3CH2OH) to a reaction mixture.What volume of ethanol should she measure out? The density of ethanol is 0.789 g cm-34.2) A saturated solution of sodium chloride is described as 0.360kg NaCl per 1kg of Water. If the densityof water is 1 g cm-3, what would be the molar concentration of saturated sodium chloride in mol dm-34.3) An oil has a density of 0.91 g cm-3. A droplet of the oil has a volume of 5.0×10-2cm3 .The approximateMrof the oil is 880. Calculate the number of molecules of oil in the droplet
Example: Blood plasma typically contains 20 parts per million(ppm) of magnesium, by mass. Calculate the mass ofmagnesium, in grams, present in 100 g of plasma.
Parts per million (ppm)Concentrations can be given also in parts per million.This is often used for gases in the atmosphere or inexhausts, and pollutants in water.=mass of substance in mixturetotal mass of mixtureX 1000 000parts per million (ppm) ofsubstance, by mass
=mass of substance in mixturetotal mass of mixtureX 1000 000parts per million (ppm) ofsubstance, by mass20 =mass of substance in mixture100X 1000 000mass of substance in mixture = 20 x100/1000 000= 2 x 10-3g5.2) A solution contains 76 ppm of a solute. Calculate the mass of the solute dissolved in 1 kg of thissolution.5.1) 1 kg of a solution contains 0.100 mol of calcium ions, Ca2+.What is the concentration ofthe calcium ions by mass in parts per million (ppm)?5.3) A solution contains 187 ppm of a solute. Calculate the mass of the solute dissolved in 0.5 kg of thissolution.