Solutions

Heterogeneous MixturesSubstances mixed with phases (heterogeneous)

Suspension: a mixture containing particles that settle out if left undisturbed Made of large particles; can be separated by

filteringColloids: heterogeneous mixtures of intermediate size cannot be separated by filtering or settling different types of colloids

solid sol (solid in solid); sol(solid in liquid); solid emulsion(liquid in solid); emulsion(liquid in liquid); solid foam(gas in solid); foam(gas in liquid); aerosol(solid in gas or liquid in gas)

Heterogeneous Mixtures : Continued

Brownian Motion: erratic movement of colloidal particlesParticles don’t settle due to collisions between particlesDestroyed by heating or adding an electrolytei.e. pollen on water

Tyndall Effect: particles scatter light Particles too small to be seen unaided Particles are large enough to scatter

light Colloids will scatter light; solution will

not Can be used to show relative [ ] of

particles in colloid ( particles have reflection)Beer’s Law: used to determine [ ]

of particles because light absorbance is related to [soln]

Compare [knowns] to [unknowns]

Write down what you observe and why it happens

What are solutions?Solutions: homogeneous mixtures Solute: dissolves Solvent: dissolving mediumcan be solid, liquid, or gasSoluble: solid dissolves in solventInsoluble: solid doesn’t dissolve in solvent

Immiscible: liquids that can’t mixMiscible: liquids that can mixSolvation: process of surrounding solute particles with solvent particles in solution In water it is called hydration“Like dissolves Like” polar dissolves polar; nonpolar

dissolves nonpolar; ionic dissolves in polar; molecular compounds could be either

Write down your observations and explain what happened and why.

Cat’s Meow Explanation

What are solutions? Continued

In order to dissolve a gas: decrease temp and increase pressure Henry’s Law: S1 = S2

P1 P2

S = solubility; P = pressure

If 0.85g of a gas at 4.0 atm of pressure dissolves in 1.0 L of water at 25C, how much will dissolve in 1 L of water at 1.00 atm of pressure and the same temperature?

Write down your observations and explain what happened. After you think the reaction is complete, hold the test tube over the sink and quickly loosen and retighten the lid. Write down your observations and explain why.

Lava Lamp Explanation

Releasing the pressure allowed more bubbles to come out of solution. Henry’s Law says that more gas dissolves at higher pressure.

What are solutions? : ContinuedFactors that affect rates of solvation Stir, surface area, temperature

Heat of solution: solvent particles move apart E required to overcome attractive forces

(endothermic) When particles mix E released (exothermic)

Solubility – maximum amount of solute that will dissolve at a given T & P (with a given solvent) Unsaturated – below maximum amount Saturated – at maximum amount Supersaturated – above maximum amount

(make saturated solution at high temp and then cool)

On graph, above line/value is super-saturated, below line/value is unsaturated

How much KNO3 can dissolve in 100 mL of water at 50C?; 200 mL

A solution contains 26.5 g NaCl in 75 g water at 20°C. Determine if the solution is unsaturated, saturated or supersaturated.

Hershey’s Kiss LabPurpose: To identify ways to increase rates of

dissolving GPS Correlation: ScSH1-7, Sc5aMaterials:

3 Hershey’s KissesWatch with second hand

Procedure:1)  Unwrap 1 Hershey’s Kiss and place it in your mouth. DO NOT CHEW IT UP OR MOVE YOUR TONGUE AROUND!! Record the amount of time it takes to allow the Kiss to dissolve completely.

 

2) Unwrap 1 Hershey’s Kiss and place it in your mouth. DO NOT CHEW IT UP!! Move your tongue around to help the Kiss dissolve. Record the amount of time it takes to allow the Kiss to dissolve completely. 3)Unwrap 1 Hershey’s Kiss and place it in your mouth. Chew the Kiss and move your tongue around to help the kiss dissolve. Record the amount of time it takes to allow the Kiss to dissolve completely.

 Observations: Make Data Table

Conclusion Questions: Copy Questions & answer them1)  In which trial did the kiss dissolve the fastest? Why?

2)List & describe the three factors that affect the solubility of a substance.

3)    Explain how the rate at which a solute dissolves can be increased.

 

Solution Concentration

Concentration: amount of solute dissolved in specific amount of solvent Ratio of solute mass to solution

mass expressed as %% mass = mass solute x 100

mass solution

3.6 g of NaCl per 100 g of water, what is the percent by mass of NaCl in the solution?

Ratio of solute volume to solutions volume expressed as %% volume = volume solute x100

volume solution

Solution Concentration: Continued Molarity (M): # of moles of solute dissolved per L solutionM = moles solute

liters of solutionIf 5.1 g of C6H12O6 is in 100.5 mL of water, what is the molarity?

To prepare a solution of a specific molarity, you put the mass of the solute into a volumetric flask and add solvent to the specific volume

How many grams of calcium chloride would you need to make 50mL of a 1M solution?

Explain in detail, how you make it.

Say“Put 5.54g CaCl2 in a 50 mL volumetric flask add water until you get to the line”

To dilute use: M1V1 = M2V2

What volume in mL, of a 2.0M CaCl2 solution would it take to make 0.50 L of a 0.300 M solution?

Solution Concentration : Continued

Molality (m) is the # moles of solute dissolved in 1 kg solventm = moles solute = moles solute

kg solvent 1000 g solvent

4.5 g of NaCl is added to 100.0 g of water. Calculate the molality.

Mole Fraction: ratio of # moles of solute in solution to the total # moles solute and solventXA = nA

nA + nB

For every 100 g of solution, 37.5 g of HCl & 62.5 g of water are used. Find the mole fraction for each component.

Colligative Properties of Solutions

Colligative properties: physical property of solutions that are affected by the number of particles but not the identity of particles

Electrolytes: ionic compounds dissociate in water to form a solution that will conduct electricity

NaCl Na+ + Cl-

1 mol NaCl(s) 1 mol Na+(aq) + Cl-(aq)

Nonelectrolytes: molecular compounds that may dissolve but don’t conduct electricity

1 mol sucrose(s) 1 mol sucrose(aq)

Colligative Properties of Solutions: Continued

Colligative properties1. Decrease vapor pressure2. Increase boiling point (when Patm =

Pvap)

Tb= Kbm (change in BP = constant (molality))

3. Decrease freezing point: solvent particles interfere with attraction of solute particlesTf= Kfm (change in FP = constant

(molality))

4. Osmosis: diffusion of solvent particles across a semipermeable membrane from [] to [] Semipermeable: allow some

particles through but not all Sometimes only water can

cross trying to equalize concentration creating a pressure called osmotic pressure

Colligative Properties of Solutions :

What is the boiling point and freezing point of a 0.029m aqueous solution of sugar? KB= 0.512C/m KF= 1.86 C/m

Need for hwEther (change from ethanol) Normal BP= 34.6 C Normal FP= -116.3C Kb= 1.79 C/m Kf= 2.02 C/m

Benzene Normal BP= 80.1 C Normal Freezing point = 5.5 C Kb= 2.53 C/m Kf= 5.12 C/m