Solutions Chapter 21 Solutions • Solution: a homogeneous mixture of 2 or more substances in the same physical state. • Properties: •Particles are small •Particles are evenly mixed •Particles will not separate • Examples: – air (nitrogen & oxygen) – Gatorade (water, sugar, etc) – NaCl(aq) (salt & water) Solution ex. Salt water Parts solvent (major in amount or does the dissolving) solute (minor in amount or being dissolved) ex. Water ex. salt Solute Solvent Type Type solid solid Solution Type solid solid liquid liquid gas solid solid liquid liquid liquid gas liquid liquid Solution Example Metal alloys ex. brass Salt water Moth balls Alcohol in water (rubbing alcohol) soda solutions Consider lemonade. 1. What is the solvent? 2. What are the solutes? https://www.youtube.com/watch?v =AedL_NCv1Pw Think about ways to dissolve sugar faster in water Factors that affect the rate of solubility (how quickly something dissolves) for solid in a liquid 1. Temperature: • T rate • T rate • Increasing temperature increases kinetic energy = increased motion 2. Surface Area (particle size): • S.A. (particle size ) rate • S.A. (particle size ) rate • Increasing surface area increases opportunity for interaction between solute and solvent 3. Stirring: • stirring rate • stirring rate • Stirring increases particle motion so more particles can be dissolved at the surface of the solid Think about ways to keep gas in coke Factors that affect the rate of solubility (how quickly something dissolves) for gas in a liquid • Keep it cold • Don’t shake it ( no stirring) • Increase pressure ( keep the cap on) • Solute: substance that is dissolved ex. sugar • Solvent: does the dissolving ex. water • Concentration: The amount of solute in a given amount of solvent • (aq) = aqueous = A solution where water is the solvent • Solubility - Ability to dissolve Types of solutions This classification is based on the amount of solute per 100g(or mL) of the solvent Types are • Unsaturated • Saturated • supersaturated Saturated solution: A solvent can not dissolve any more solute Definitions Solutions can be classified as saturated or unsaturated. A saturated solution contains the maximum quantity of solute that dissolves at that temperature. An unsaturated solution contains less than the maximum amount of solute that can dissolve at a particular temperature Definitions https://www.google.com/search?q=adding+a+seed+crystal+to+a+supersaturated+sol ution&oq=adding+a+seed+cr&aqs=chrome.1.69i57j0.11023j0j7&sourceid=chrome&i e=UTF-8#kpvalbx=1 https://www.youtube.com/watch?v=1y3bKIOkcmk SUPERSATURATED SOLUTIONS contain more solute than is possible to be dissolved Supersaturated solutions are unstable. The super saturation is only temporary , unstable and usually accomplished in one of two ways: 1. Warm the solvent so that it will dissolve more, then cool the solution 2. Evaporate some of the solvent carefully so that the solute does not solidify and come out of solution. Types of solutions • Unsaturated = amount in the Q is less than the graph says • Saturated= amount in the Q = to the graph says • Supersaturated = amount in the Q is greater than the graph says Solubility curves 30oC? 90g /100g of water at 50oC? 30o 30o C? 30o C? C 70g70g supersaturated 50oC or 49oC NaCl KNO3 46oC unsaturated Bellringer 8 (Refer to the board if you forgot how to do these) 1.Calculate the molar mass (GFM) of Ca(NO2)2 2.How many moles is present in 250g of Ca(NO2)2? Molarity Also known as molar concentration, molarity (M) is the number of moles of solute (the material dissolved) per liter of solution. • Molarity = M=mole/Liter of solution, M= mol/L • Mole = mol=mass/molar mass, mol=m/mm • Molar mass(mm) = add the mass of the atoms together • Concentrated solution has more solute dissolved in the solvent than a dilute solution. • Molarity by dilution M1V1 = M2V2 (Concentrated ) = (diluted) 15.What is the volume of a 0.250 M NaHCO3 solution that contains 16.8 g NaHCO3? 16. M1V1=M2V2 17. What volume of 6.0 M HNO3 would be needed to prepare 600 mL of 0.100 M HNO3? How much concentrated 18 M sulfuric acid is needed to prepare 250.0 mL of a 6.0 M solution? • How much concentrated 12 M hydrochloric acid is needed to prepare • 100.0 mL of a 2.0 M solution? Electrolyte vs Nonelectrolyte •Electrolyte –Compounds that produces solutions of ions that conduct electricity in water. ex. Ionic compounds (NaCl)and polar covalent compounds (HCl) •Non electrolyte – substances that form no ions in water and cannot conduct electricity ex. Non polar covalent compounds.(oil or fat and hydrocarbons) Solutions as Electrolytes https://www.youtube.com/watch?v=3LR4K10d8TA https://www.youtube.com/watch?v=1XWnovm6JLs •Strong conductor = strong electrolyte •Weak conductor = weak electrolyte •No conductor - nonelectrolyte ionization ionization –the process in which molecular (covalent) compounds dissolve in water and form charged particles. Ex. HCl + H2O H3O+ + Cl- Ion : Is an atom or group of atoms having a charge ionization ionization –the process in which molecular compounds dissolve in water and form charged particles. Ex. HCl + H2O H3O+ + Cl- Dissolving sugar in water Hydrogen Bond • Attraction between a hydrogen atom and an atom such as oxygen or nitrogen that is either part of another molecule or located at a distant site on the same molecule. • Both the hydrogen atom and the other atom must be involved in a polar covalent bond Hydrogen bond between water and ethanol Dissociation Dissociation - the process in which an ionic solid separates into positive and negative ions NaCl Na + + ClDissolving salt in water or hydration Ionic Compounds in Water •The positive ends of a water molecule are attracted to negative ions and the negative ends are attracted to positive cations in an ionic compound – this is called hydration. •The ions become hydrated & move around independently. Effect of solute •Lowering freezing point Ex. Road salt •Raising boiling point Ex. Car radiators have antifreeze Freezing point depression and boiling point elevation: adding solute to a solvent lowers the freezing point and raises the boiling point of the solvent. • Solute particles disrupt crystallization and evaporation. • The change in freezing point or boiling point is directly proportional to the molarity of solute particles. • A solute that produces more ions in solution has the greatest effect. Water is known as the universal solvent •One of the most valuable properties of water is its ability to dissolve. •Water is polar thus having positive & negative partial charges on its ends. •So it can dissolve ionic compounds and polar covalent compounds. Covalent Compounds in Water •Water also dissolves many nonionic substances such as ethanol (C2H5OH). •The reason for this is that ethanol is also polar. •Polar dissolves polar – “like dissolves like”. •This is the reason water will not dissolve oil. •Non polar dissolves in non polar Non polar solvents: Properties •Mainly hydrocarbons [CxHy](fuels) •Toxic •flammable How does soap works? • Molecules that readily mix with water are hydrophilic. (hydro=water and philic=loving) Molecules that readily mix with oil are hydrophobic. (phobic=fearing) • Soap can mix with both water and with oil. Why? The soap molecule has two different ends, one that is hydrophilic (polar head) that binds with water and the other that is hydrophobic (nonpolar hydrocarbon tail) that binds with grease and oil. How does soap works? Versatile molecules •Some substances are versatile because they have a non polar and a polar end. •Ex. Sodium stearate has a non polar and a polar end. It is an important ingredient in soap. •Ex. Alcohols . They have a general formula CxHyOH (x and y are subscripts) Solutes and Solvents Polar Water Ionic Polar covalent Vitamin B& C Nonpolar Oil Fat Dirt Vitamin A Dry cleaning solvent Iodine Versatile Alcohol Soap detergent Vitamins •Some vitamins are non polar (vitamin A) and dissolve in fat. •Other vitamins are polar (vitamin B&C) dissolves in water. •Which vitamins we should intake more ? Why?
