Chemistry Review Unit 1C

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Chemistry Review Unit 1C D

• Investigating the Fish Kill and Cleaning Water

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Solutions

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

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Three States of Solubility
supersaturated
saturated
unsaturated
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Types of Solutions

• Unsaturated
• cant see solute
• can add more solute
• under the curve

• Saturated
• cant see solute
• full
• on the curve

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Types of Solutions

• Supersaturated
• cant see solute (but will precipitate out when
  cooled)
• needs to be heated
• over full
• above the curve

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Reading Solubility Curves

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

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Problem Type I
What kind of a solution do I have when 55g of
NaCl is dissolved in 100 ml of water at 47ºC?
Point falls above the NaCl solubility curve!.
supersaturated
If only 33 grams of salt was dissolved?
unsaturated
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Problem Type II
To make a saturated solution of KCl at 50ºC,
how much KCl would I add to 100 grams of water?
42g
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Problem Type III
But what if I dont 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
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Problem Type IV
At which temperature will 80grams of KNO3
dissolve in 100ml of water and make a saturated
solution?
49ºC
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Gas Solubility Curves

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

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Solute Concentration
Amount of solute

Concentration
100
x
Amount of solution
solute
solute solvent
IMPORTANT Amount of solution solute solvent
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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
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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

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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

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Polarity
Polar - two poles ( and -) Ex. Water
Nonpolar - no charges or poles Ex. Oil
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Drawings of Dissolved Ionic Substances
Unsaturated
Saturated
Supersaturated
Oxygen (head) - pink - ion Hydrogen (ears)
yellow ion
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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
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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

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Heavy Metals

• Sources
• paint
• thermometers
• mines
• Damages
• brain
• proteins
• eyes

• Charged ions so can dissolve in water
• Examples
• Lead
• Mercury
• Cadmium

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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
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Alternative Cleaning Methods

• Ozone/UV -
• pros no extra chemicals in water, no THMs
• cons bacteria can form later, costly
• Charcoal Filter
• pros cleans the best, no THMs
• cons bacteria can form later, costly
• No pre-chlorination
• pros less THMs
• cons not as clean

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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

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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