standard 6: solutions chapter 16
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Standard 6: Solutions chapter 16. Chemistry Ms. Siddall. Standard 6a: solution definitions. 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: - PowerPoint PPT PresentationTRANSCRIPT
Standard 6: Solutionschapter 16
ChemistryMs. Siddall
Standard 6a: solution definitions• 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)
Summary 1
• Is muddy water a solution? Why/why not?
• Solute: substance that is dissolved e.x. sugar
• Solvent: does the dissolving e.x. water
• Concentration: The amount of solute in a given amount of solvent e.x. [HCl]
• (aq) = aqueous = A solution where water is the solvent
Summary 2
Consider lemonade.
1. What is the solvent?
2. What are the solutes?
• Solvent: H2O molecules with dipole
• Solute: Ionic crystal lattice
Standard 6b: Dissolving Process
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+
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• Polar H2O molecules surround positive and negative ions and break apart crystal lattice
• Water molecules move away (diffusion) so the process is repeated
Show animation
Summary 3
Explain how water dissolves ionic compounds
• It takes energy to break bonds
NaCl(s)
NaCl(aq)en
erg
y
Energy needed to overcome
lattice energyEnergy
released during
dissolvingDissolving
Summary 4
Does the energy diagram for dissolving NaCl represent anendothermic or exothermic process? Explain your answer.
Saturated solution: A solvent can not dissolve any more solute
• A saturated solution is at equilibrium. Particles are dissolving and precipitating at the same rateNaCl(s) Na+
(aq) + Cl-(aq)
Summary 5
Does the dissolving process stop at equilibrium? Explain why/why not.
• Some factors affect solubility (how much solute is dissolved)
• Some factors affect rate (how fast solute is dissolved)
• Some factors affect rate and solubility
Standard 6c: Factors that affect the dissolving process
Standard 6c: Factors that affect the dissolving process
Factors affecting how much solute is dissolved
1. Type of solvent / solute
• Polar solvents dissolve polar & ionic solutes
• Non-polar solvents dissolve non-polar & covalent solutes
e.x oil and water do not mix
Summary 6
Is oil a polar compound or a non polar compound? How do you know?
2. Temperature• For solids: Temperature solubility
Temperature increases kinetic energy of solvent particles therefore more solute can be dissolved
• For gases: Temperature solubility Temperature increases the kinetic energy of solute particles therefore more particles escape from solution
Summary 7
Why does the solubility of gas in solution decrease with increasing temperature?
Solubility of solids & gases
3. Pressure (Gasses Only!)
• Increasing pressure forces more gas into solution
• Pressure solubility • Pressure solubility
High pressure
low pressure
solution
air
Gas
Summary 8
Does the concentration of carbon dioxide in your soda increase or decrease when you open the bottle? Why?
Factors that affect the rate of solubility (how quickly something dissolves)
1. Temperature:
• T rate • T rate • Increasing temperature increases kinetic
energy = increased motion = increased diffusion
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
Summary 9
1. Name one factor that affects only solubility
2.Name one factor that affects only rate
3.Name one factor that affects rate and solubility
Standard 6d: calculations• Molarity (mol/L)Molarity = Moles solute Liters solution • Grams per Liter (g/L)
= Grams solute
Liters solution
• Percent Composition (%)
grams solute x 100%
grams solution• Parts Per Million (ppm)
grams solute x 106
grams solution
Summary 10
A solution contains 80g of NaOH in 500ml of solution. Calculate:
1.‘grams per liter’2. Molarity3. percent composition for the solution
• Using ‘Parts per Million’ (ppm)• Usually used to measure solutions
containing a small amount of solute • e.x air quality or drinking water quality
– Air contains about 1ppm CO2 (Every 1million grams of air contains 1g CO2)
• smaller concentrations are measured in ppb(parts per billion)– Drinking water usually contains ≤ 0.5 ppb lead
Summary 11
Which solution has the highest concentration of fluoride ions?a) 10 ppm F-
b) 100 ppm F-
c) 10 ppb F-
d) 100 ppb F-
• Example: What is the concentration (ppm) of a 1L solution containing 5mg arsenic?
(The density of aqueous solutions = 1g/ml)
Standard 6e: effect of solute on freezing and boiling point.
Molality (m) = moles solute Kg
solvent
e.x. what is the molality of a solution made by dissolving 180g sugar (C6H12O6) in 500g water?
180g sugar
500g water 180g sugar
1 mol sugar 1000g
1 kg= 2m
Summary 18
what is the molality of a solution made by dissolving 92g ethanol (C2H6O) in 200g water?
92g ethanol
200g water 46g ethanol
1 mol ethanol 1000g
1 kg= 20m
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 molality of solute particles.
• A solute that produces more ions in solution has the greatest effect.
Summary 19
Explain why it takes more energy to boil water when it has more solute particles dissolved in solution.
3m sugar
3 moles NaCl produces 6m of solute particles
3moles CaCl2 produces 9m of solute particles
Summary 19
Which will affect the boiling point of solution more? WHY?
a) 1m NaClb) 1m CaCl2c) 1m AlCl3
6f: Chromatography and distillation.
Chromatography: the separation of solution into individual substances using differences in polarity.
e.x. DNA analysis
Distillation: separation of solutions into individual substances using differences in physical properties (boiling point)
e.x. salt water can be purified by distillation
Summary 20
Why is it possible to separate alcohols by distillation?