Solutions
Download
1 / 34

Solutions - PowerPoint PPT Presentation


  • 277 Views
  • Updated On :

Solutions. Solutions. A solution is a homogeneous mixture. A solution is composed of a solute dissolved in a solvent . Solutions exist in all three physical states:. Gases in Solution. Temperature effects the solubility of gases.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Solutions' - carson


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Solutions2 l.jpg
Solutions

  • A solution is a homogeneous mixture.

  • A solution is composed of a solute dissolved in a solvent.

  • Solutions exist in all three physical states:


Gases in solution l.jpg
Gases in Solution

  • Temperature effects the solubility of gases.

  • The higher the temperature, the lower the solubility of a gas in solution.

  • An example is carbon dioxide in soda:

    • Less CO2 escapes when you open a cold soda than when you open the soda warm


Polar molecules l.jpg
Polar Molecules

  • When two liquids make a solution, the solute is the lesser quantity, and the solvent is the greater quantity.

  • Recall, that a net dipole is present in a polar molecule.

  • Water is a polar molecule.


Polar nonpolar solvents l.jpg
Polar & Nonpolar Solvents

  • A liquid composed of polar molecules is a polar solvent. Water and ethanol are polar solvents.

  • A liquid composed of nonpolar molecules is a nonpolar solvent. Hexane is a nonpolar solvent.


Like dissolves like l.jpg
Like Dissolves Like

  • Polar solvents dissolve in one another.

  • Nonpolar solvents dissolve in one another.

  • This it the like dissolves like rule.

  • Methanol dissolves in water but hexane does not dissolve in water.

  • Hexane dissolves in toluene, but water does not dissolve in toluene.


Miscible immiscible l.jpg
Miscible & Immiscible

  • Two liquids that completely dissolve in each other are miscible liquids.

  • Two liquids that are not miscible in each other are immiscible liquids.

  • Polar water and nonpolar oil are immiscible liquids and do not mix to form a solution.


Solids in solution l.jpg
Solids in Solution

  • When a solid substance dissolves in a liquid, the solute particles are attracted to the solvent particles.

  • When a solution forms, the solute particles are more strongly attracted to the solvent particles than other solute particles.

  • We can also predict whether a solid will dissolve in a liquid by applying the like dissolves like rule.


Like dissolves like for solids l.jpg
Like Dissolves Like for Solids

  • Ionic compounds, like sodium chloride, are soluble in polar solvents and insoluble in nonpolar solvents.

  • Polar compounds, like table sugar (C12H22O11), are soluble in polar solvents and insoluble in nonpolar solvents.

  • Nonpolar compounds, like naphthalene (C10H8), are soluble in nonpolar solvents and insoluble in polar solvents.


The dissolving process l.jpg
The Dissolving Process

  • When a soluble crystal is placed into a solvent, it begins to dissolve.

  • When a sugar crystal is placed in water, the water molecules attack the crystal and begin pulling part of it away and into solution.

  • The sugar molecules are held within a cluster of water molecules called a solvent cage.


Dissolving of ionic compounds l.jpg
Dissolving of Ionic Compounds

  • When a sodium chloride crystal is place in water, the water molecules attack the edge of the crystal.

  • In an ionic compound, the water molecules pull individual ions off of the crystal.

  • The anions are surrounded by the positively charged hydrogens on water.

  • The cations are surrounded by the negatively charged oxygen on water.


Rate of dissolving l.jpg
Rate of Dissolving

  • There are three ways we can speed up the rate of dissolving for a solid compound.

  • Heating the solution:

    • This increases the kinetic energy of the solvent and the solute is attacked faster by the solvent molecules.

  • Stirring the solution:

    • This increases the interaction between solvent and solute molecules.

  • Grinding the solid solute:

    • There is more surface area for the solvent to attack.


Solubility and temperature l.jpg
Solubility and Temperature

  • The solubility of a compound is the maximum amount of solute that can dissolve in 100 g of water at a given temperature.

  • In general, a compound becomes more soluble as the temperature increases.


Saturated solutions l.jpg
Saturated Solutions

  • A solution containing exactly the maximum amount of solute at a given temperature is a saturated solution.

  • A solution that contains less than the maximum amount of solute is an unsaturated solution.

  • Under certain conditions, it is possible to exceed the maximum solubility of a compound. A solution with greater than the maximum amount of solute is a supersaturated solution.


Supersaturated solutions l.jpg
Supersaturated Solutions

  • At 55C, the solubility of NaC2H3O2 is 100 g per 100 g water.

  • If a saturated solution at 55C is cooled to 20C, the solution is supersaturated.

  • Supersaturated solutions are unstable. The excess solute can readily be precipitated.


Supersaturation l.jpg
Supersaturation

  • A single crystal of sodium acetate added to a supersaturated solution of sodium acetate in water causes the excess solute to rapidly crystallize from the solution.


Concentration of solutions l.jpg
Concentration of Solutions

  • The concentration of a solution tells us how much solute is dissolved in a given quantity of solution.

  • We often hear imprecise terms such as a “dilute solution” or a “concentrated solution”.

  • There are two precise ways to express the concentration of a solution:

    • mass/mass percent

    • molarity


Mass percent concentration l.jpg

mass of solute

g solute

× 100% = m/m %

mass of solution

× 100% = m/m %

g solute + g solvent

Mass Percent Concentration

  • Mass percent concentration compares the mass of solute to the mass of solvent.

  • The mass/mass percent (m/m %) concentration is the mass of solute dissolved in 100 g of solution.


Calculating mass mass percent l.jpg

5.50 g NaCl

× 100% = m/m %

5.00 g NaCl + 97.0 g H2O

5.00 g NaCl

× 100% = 4.90 %

102 g solution

Calculating Mass/Mass Percent

  • A student prepares a solution from 5.00 g NaCl dissolved in 97.0 g of water. What is the concentration in m/m %?


Mass percent unit factors l.jpg

100 g solution

100 g solution

4.90 g NaCl

95.1 g water

100 g solution

100 g solution

4.90 g NaCl

95.1 g water

95.1 g water

4.90 g NaCl

95.1 g water

4.90 g NaCl

Mass Percent Unit Factors

  • We can write several unit factors based on the concentration 4.90 m/m% NaCl:


Mass percent calculation l.jpg

100 g solution

25.0 g sucrose ×

= 500 g solution

5.00 g sucrose

Mass Percent Calculation

  • What mass of a 5.00 m/m% solution of sucrose contains 25.0 grams of sucrose?

  • We want grams solution, we have grams sucrose.


Molar concentration l.jpg

moles of solute

= M

liters of solution

Molar Concentration

  • The molar concentration, or molarity (M), is the number of moles of solute per liter of solution, is expressed as moles/liter.

  • Molarity is the most commonly used unit of concentration.


Calculating molarity l.jpg

1 mol NaOH

18.0 g NaOH

×

= 4.50 M NaOH

40.00 g NaOH

0.100 L solution

Calculating Molarity

  • What is the molarity of a solution containing 18.0 g of NaOH in 0.100 L of solution?

  • We also need to convert grams NaOH to moles NaOH (MM = 40.00 g/mol).


Molarity unit factors l.jpg

1 L solution

4.50 mol NaOH

1 L solution

4.50 mol NaOH

1000 mL solution

4.50 mol NaOH

1000 mL solution

4.50 mol NaOH

Molarity Unit Factors

  • We can write several unit factors based on the concentration 4.50 M NaOH:


Molar concentration problem l.jpg

0.100 mol K2Cr2O7

294.2 g K2Cr2O7

×

250.0 mL solution ×

1000 mL solution

1 mol K2Cr2O7

Molar Concentration Problem

  • How many grams of K2Cr2O7 are in 250.0 mL of 0.100 M K2Cr2O7?

  • We want mass K2Cr2O7, we have mL solution.

= 7.36 g K2Cr2O7


Molar concentration problem26 l.jpg

1 mol HCl

1000 mL solution

7.30 g HCl ×

×

36.46 g HCl

12.0 mol HCl

Molar Concentration Problem

  • What volume of 12.0 M HCl contains 7.30 g of HCl solute (MM = 36.46 g/mol)?

  • We want volume, we have grams HCl.

= 16.7 mL solution


Dilution of a solution l.jpg
Dilution of a Solution

  • Rather than prepare a solution by dissolving a solid in water, we can prepare a solution by diluting a more concentrated solution.

  • When performing a dilution, the amount of solute does not change, only the amount of solvent.

  • The equation we use is: M1 × V1 = M2 × V2

    • M1 and V1 are the initial molarity and volume and M2 and V2 are the new molarity and volume


Dilution problem l.jpg

(0.10 M) × (5.00 L)

V1 =

= 0.083 L

6.0 M

Dilution Problem

  • What volume of 6.0 M NaOH needs to be diluted to prepare 5.00 L if 0.10 M NaOH?

  • We want final volume and we have our final volume and concentration.

    M1 × V1 = M2 × V2

    (6.0 M) × V1 = (0.10 M) × (5.00 L)


Solution stoichiometry l.jpg

balanced

equation

solution

concentration

molar mass

Solution Stoichiometry

  • In Chapter 10, we performed mole calculations involving chemical equations, stoichiometry problems.

  • We can also apply stoichiometry calculations to solutions.

    molarity known  moles known 

    moles unknown  mass unknown


Solution stoichiometry problem l.jpg

187.77 g AgBr

0.100 mol AlBr3

3 mol AgBr

37.5 mL soln ×

×

×

1 mol AgBr

1000 mL soln

1 mol AlBr3

Solution Stoichiometry Problem

  • What mass of silver bromide is produced from the reaction of 37.5 mL of 0.100 M aluminum bromide with excess silver nitrate solution?

    AlBr3(aq) + 3 AgNO3(aq) → 3 AgBr(s) + Al(NO3)3(aq)

  • We want g AgBr, we have volume of AlBr3

= 2.11 g AgBr


Conclusions l.jpg
Conclusions

  • Gas solubility decreases as the temperature increases.

  • Gas solubility increases as the pressure increases.

  • When determining whether a substance will be soluble in a given solvent, apply the like dissolves like rule.

    • Polar molecules dissolve in polar solvents.

    • Nonpolar molecules dissolved in nonpolar solvents.


Conclusions continued l.jpg
Conclusions Continued

  • Three factors can increase the rate of dissolving for a solute:

    • Heating the solution

    • Stirring the solution

    • Grinding the solid solute

  • In general, the solubility of a solid solute increases as the temperature increases.

  • A saturated solution contains the maximum amount of solute at a given temperature.


Conclusions continued33 l.jpg

moles of solute

= M

liters of solution

mass of solute

× 100% = m/m %

mass of solution

Conclusions Continued

  • The mass/mass percent concentration is the mass of solute per 100 grams of solution:

  • The molarity of a solution is the moles of solute per liter of solution.


Conclusions continued34 l.jpg
Conclusions Continued

  • You can make a solution by diluting a more concentrated solution:

    M1 × V1 = M2 × V2

  • We can apply stoichiometry to reactions involving solutions using the molarity as a unit factor to convert between moles and volume.


ad