2.3 Solutions2.3 Solutions

ObjectivesObjectives

9.9. Define solution, solute, solvent, and Define solution, solute, solvent, and concentrationconcentration

10.10. Explain the dissociation of waterExplain the dissociation of water

11.11. Contrast properties of acids and Contrast properties of acids and basesbases

12.12. Describe the use of pH scaleDescribe the use of pH scale

13.13. Explain the action of buffersExplain the action of buffers

Obj 9: Obj 9: Define solution, solute, Define solution, solute, solvent, and concentrationsolvent, and concentration

SolutionSolution – mixture of one or more – mixture of one or more substances that are uniformly substances that are uniformly distributed in another substancedistributed in another substance

SoluteSolute – substance dissolved in solution – substance dissolved in solution

SolventSolvent – substance in which the solute – substance in which the solute is dissolvedis dissolved

ExampleExampleSugar – soluteSugar – soluteWater – solventWater – solventMixed = solution of sugar waterMixed = solution of sugar water

Neither sugar or water molecules are Neither sugar or water molecules are altered chemicallyaltered chemically

If solution boiled, sugar would remainIf solution boiled, sugar would remain

Solutions vary in Solutions vary in concentrationconcentration – – measurement of amount of solute dissolved in measurement of amount of solute dissolved in fixed amount of solutionfixed amount of solution

ExampleExample2% saltwater solution = 2 g of salt dissolved 2% saltwater solution = 2 g of salt dissolved

in enough water to make 100 mL of solutionin enough water to make 100 mL of solutionMore solute the greater the %More solute the greater the %

Saturated solutionSaturated solution – one in which no more – one in which no more solute can dissolvesolute can dissolve

Aqueous solutionsAqueous solutions – solutions in which – solutions in which water is the solventwater is the solvent

ExampleExampleMarine organisms – the seaMarine organisms – the seaPlants get nutrients from aqueous Plants get nutrients from aqueous

solutionsolutionBody cells in aqueous solutionBody cells in aqueous solution

Obj 10: Obj 10: Explain the Explain the dissociation of waterdissociation of water

DissociationDissociation – breaking apart of the – breaking apart of the water molecules into 2 ions of opposite water molecules into 2 ions of opposite chargecharge

ExampleExampleHH22O O ↔ H↔ H++ + OH + OH--

Forms 2 ionsForms 2 ionsHH++ and OH and OH--

Hydroxide ion = OH-Hydroxide ion = OH-

The free H+ ion can react with other water The free H+ ion can react with other water moleculemoleculeHH++ + H + H22O O ↔ H↔ H33OO++

HH33OO+ + = hydronium ion= hydronium ionAcidity or Alkalinity measure of relative Acidity or Alkalinity measure of relative

amounts of hydronium and hydroxide ions amounts of hydronium and hydroxide ions If hydronium ions = hydroxide ions the If hydronium ions = hydroxide ions the

solution is neutralsolution is neutralPure waterPure water

Obj 11: Obj 11: Contrast properties of Contrast properties of acids and basesacids and bases

AcidAcid - # of hydronium ions greater than - # of hydronium ions greater than hydroxide ions in a solutionhydroxide ions in a solution

ExampleExampleHCl – hydrogen chloride – a gas dissolved in HCl – hydrogen chloride – a gas dissolved in

water water Molecules dissociate for form HMolecules dissociate for form H+ + and Cland Cl--

HCl HCl ↔ H↔ H++ + Cl + Cl--

Free H+ combine with waterFree H+ combine with waterH+ + HH+ + H22O O ↔ H↔ H33O+O+

Solution has more hydronium ions Solution has more hydronium ions (H(H33O+) than hydroxide ions (OH-) = O+) than hydroxide ions (OH-) = acidic solutionacidic solution

Acids have sour tasteAcids have sour tasteConcentrated forms are highly corrosiveConcentrated forms are highly corrosive

BaseBase – solution contains more hydroxide – solution contains more hydroxide ions than hydronium ionsions than hydronium ions

NaOH NaOH ↔ Na↔ Na++ + OH + OH--

Alkaline Alkaline - refers to bases, an adjective - refers to bases, an adjectiveTaste bitterTaste bitterFeel slipperyFeel slippery

Acids and BasesAcids and Bases

Obj 12: Obj 12: Describe the use of pH Describe the use of pH scalescale

Compares relative concentrations of Compares relative concentrations of hydronium (Hhydronium (H33OO++) and hydroxide (OH) and hydroxide (OH--) )

ionsionsRanges from 0-14 fig 2-10Ranges from 0-14 fig 2-100 = very acidic0 = very acidic7= neutral7= neutral14 = very basic14 = very basic

Ammonia = 11.5Ammonia = 11.5 Internal fluid = 8Internal fluid = 8Blood = 7.5Blood = 7.5Water = 7Water = 7Urine = 6Urine = 6Vinegar = 3Vinegar = 3Stomach acid = 2Stomach acid = 2

Measure on logarithmic scaleMeasure on logarithmic scaleEach unit is a ten fold changeEach unit is a ten fold changeExampleExample

pH of 4 has 10 x more hydronium ions pH of 4 has 10 x more hydronium ions (H(H33OO++) than a solution with a pH of 5) than a solution with a pH of 5

100 x more hydronium ions (H100 x more hydronium ions (H33OO++) than ) than

a solution with a pH of 6a solution with a pH of 6

Measure with litmus paperMeasure with litmus paperColor changes with pHColor changes with pH

pH ScalepH Scale

Obj 13: Obj 13: Explain the action of Explain the action of buffersbuffers

Chemical substances that neutralize Chemical substances that neutralize small amounts of either an acid or base small amounts of either an acid or base added to a solutionadded to a solution

Buffers maintain internal fluids at normal Buffers maintain internal fluids at normal and safe levelsand safe levels

Review ObjectivesReview Objectives

9.9. Define solution, solute, solvent, and Define solution, solute, solvent, and concentrationconcentration

10.10. Explain the dissociation of waterExplain the dissociation of water

11.11. Contrast properties of acids and Contrast properties of acids and basesbases

12.12. Describe the use of pH scaleDescribe the use of pH scale

13.13. Explain the action of buffersExplain the action of buffers