Chemistry Review Unit 1C & D

Chemistry Review Unit 1C & D Investigating the Fish Kill and Cleaning Water

Solutions • Homogeneous • Equally distributed • solute -- what is dissolved (Ex. Salt) • solvent - what dissolved (Ex. Water = most common)

Three States of Solubility supersaturated saturated unsaturated

Unsaturated can’t see solute can add more solute under the curve Saturated can’t see solute “full” on the curve Types of Solutions

Types of Solutions • Supersaturated • can’t see solute (but will precipitate out when cooled) • needs to be heated • “over full” • above the curve

Reading Solubility Curves • Solute ALWAYS goes on top of fraction • Water ALWAYS goes on bottom of fraction • Graph ratio is ALWAYS over 100

Problem Type I What kind of a solution do I have when 55g of NaCl is dissolved in100 mlof water at 47ºC? Point falls above the NaCl solubility curve!. supersaturated If only 33 grams of salt was dissolved? unsaturated

Problem Type II To make a saturated solution of KCl at 50ºC, how much KCl would I add to 100 grams of water? 42g

Problem Type III But what if I don’t use 100 grams of water? Then use ratios. How much KCl can dissolve in 160 g of water at 52oC? 46 g KCl_ = x g KCl100 g H2O 160 g H2O (46)(160) = 100x X = 73.6 g

Problem Type IV At which temperaturewill 80grams of KNO3 dissolve in 100ml of water and make a saturated solution? 49ºC

Gas Solubility Curves • Solid - Solubility increases as temp. increases • Gas -Solubility decreases as temp. increases • Gas - Solubility increases as pressure increases

Solute Concentration Amount of solute Concentration = 100% x Amount of solution solute solute + solvent IMPORTANT Amount of solution = solute + solvent

Concentration Problem What is the percent concentration of salt if 38g of NaCl is dissolved in 153ml of water? 38 19.90% x 100 = (153 + 38) salt solution

Concentration Problem • If I have a 20% solution of NaCl what is its • concentration in • pph? • 20 (20/100) • ppt? • 20 = x • 100 1000 x = 200 • ppm?? • 20 = x • 100 1,000,000 x = 200,000

How does water dissolve ionic compounds? • Positive side of water attracts negative ion and surrounds it • Water molecules “pull” until ion is free and completely surrounded by water • Same happens with negative side of water and positive ion in compound

Polarity Polar - two poles (+ and -) Ex. Water Nonpolar - no charges or poles Ex. Oil

Drawings of Dissolved Ionic Substances Unsaturated Saturated Supersaturated Oxygen (head) = - pink = - ion Hydrogen (ears) = + yellow = + ion

Likes Dissolve Likes “ POLAR WILL DISSOLVE IN OTHER POLAR” “NONPOLAR WILL DISSOLVE IN OTHER NONPOLAR” “POLAR DOES NOT DISSOLVE IN NONPOLAR AND VICE VERSA” so...water & oil don't mix

pH • Tells whether it is an acid, base, or neutral • 1-6 = acid (more H+ ions) • ex. HCl, H2SO4 • 7 = neutral • ex. NaCl, H2O • 8-14 = base (more OH- ions) • ex. NaOH, Ba(OH)2

Heavy Metals • Sources • paint • thermometers • mines • Damages • brain • proteins • eyes • Charged ions so can dissolve in water • Examples: • Lead • Mercury • Cadmium

Water Cleaning • Steps to cleaning • pre-chlorination - kills bacteria • flocculation - removes solid materials • post-chlorination - keeps new bacteria from growing • aeration - improves taste • Problems - - Caused by Cl- + organic molecules THM's

Alternative Cleaning Methods • Ozone/UV - • pros = no extra chemicals in water, no THM’s • cons = bacteria can form later, costly • Charcoal Filter • pros = cleans the best, no THM’s • cons = bacteria can form later, costly • No pre-chlorination • pros = less THM’s • cons = not as clean

Water Softening • Hard = Ca2+ -- turns cloudy with Na2CO3, less soap suds • Ion Exchange Resin • switches Ca2+ for 2Na+ • Calgon • forms LARGE molecule and binds up Ca 2+

Fishkill • Organic Carbon • due to plants and algae • more C, less oxygen • Phosphates and Nitrates • fertilizer • more Phosphorous and Nitrates = more plants • Dissolved Oxygen • needed in right amount for fish to survive • more temperature, less oxygen

Chemistry Review Unit 1C & D