Chapter 15
How do you separate a homogeneous mixture ?
What about heterogeneous?
Homogeneous mixtures can be separated via distillation
Heterogeneous mixtures can be separated via filtration
Define: Solvent and Solute
Solvent: Dissolving medium
Solute: Substance being dissolved.
Using the equation M = n/L
What is the Molarity of a solution that uses 100.0 g of NaCl dissolved in 5.00 liters of water.
M= 1.71 moles of NaCl / 5 liters
M= 0.342 moles / Liter
What is the difference between heat and temperature?
Heat is the flow of energy from one substance to another.
Temperature is a measure of the average kinetic energy of a substance.
How many joules are in 155 calories?
155 cal x ( 4.184 J / 1 cal) = 649 J
What is a difference between solutions, colloids, and suspensions?
Particle size / uniformity / tyndall effect
Solution >1 nm
Colloids < 1nm > 1000nm
Suspension > 1000nm
Define electrolyte and non-electrolyte
Compound that conducts current when it is in an aqueous solution or in the molten state. All ionic compounds are electrolytes.
Electrolyte : ionic compounds
Non-electrolyte : most covalent compounds
Using this equation: M1 x V1 = M2 x V2
How many milliliters of aqueous 2.00 M MgSO4 must be diluted with water to prepare 100.0 mL of aqueous 0.400 M MgSO4?
2.00M x V1 = 0.400 M x 100.0mL
V1= (0.400M x 100.0mL ) / 2.00 M
V1= 20.0 mL
List three endothermic phase changes
List three exothermic phase changes
Endothermic: Melting, vaporization sublimation
Exothermic: Freezing, condensation, deposition
How many kilojoules are in 1 Calorie?
1 Calorie x ( 1000 calorie/ 1 Cal ) x ( 4.184 J/ 1 cal) x ( 1 Kilojoule / 1000 joule) = 4 KJ
Write the balanced equation for the dissociation of Lithium sulfide
Li2S --> 2Li + S
Define miscible, and immiscible.
Miscible: liquids that dissolve in one another in all proportions
Immiscible: liquids that do not dissolve.
Using the equation S1/P1= S2/P2
If the solubility of a gas in water is 0.77 g/L at 3.5 atm, what is its solubility (in g/L ) if the pressure is decreased to 1.0 atm
( 0.77 g/L ) / 3.5 atm = S2 / 1.0 atm
(( 0.77 g/L ) / 3.5 atm) x 1.0 atm = S2
S2= 0.22 g/L
If the molar heat of fusion for a substance is 44.0 kl/mol , what would the molar heat of solidification be for the same substance?
-44.0 KJ/mol
In a calorimeter, water has a mass of 150 g and a specific heat capacity of 4.184 (Joules/ gram x Celsius). If a chemical reaction increases the temp of water from 20.0 C to 80.0 C, how much heat has been transferred (q) ?
q = 150 g x (4.184 J/g x C ) x 60.0 C
q= 38000 J
What is the Tyndall Effect?
Between solutions, colloids, and suspensions, which of these is the Tyndall effect present?
The scattering of visible light by colloid or suspension particles
Process that occurs when ionic compounds dissolve. Solvent molecules surround the positive and negative ions.
In lab, Mr. Nelson wants to create a 12.0 M solution of HCl in 10.0 L of water.
First figure out how much HCl (in grams) is needed to do this.
Second, figure out the new Molarity of the diluted solution if 8.00 L of water is added.
1) 12.0M = moles HCl / 10.0L
moles HCl needed = 1.20 x 102 moles
1.20 x 102 moles HCl x ( 36.46 g / 1 mole HCl)
= 4,380 g HCl
2) 12.0 M x 10.0 L = M2 x 18.0 L
( 12.0 M x 10.0 L ) / 18.0 L = M2
M2 = 6.67 M
List and describe the 3 types of heat transfer.
Conduction - Heat transfer via direct contact.
Convection- heat transfer through the mixing of liquids/gasses
Radiation- heat transfer through electromagnetic waves.
The molar heat of fusion for water is 6.01 KJ/mol
How much heat in joules is needed to heat 14.0 grams of H2O from 0 Celsius as an ice, to 0 Celsius as a liquid?
14.0 g H2O x ( 1 mole H2O / 18.0 g H2O ) x ( 6.01 KJ / 1 mole H2O ) x ( 1000 J / 1 KJ ) = 4670 J
List and describe three ways to speed up a substance rate of dissolving.
1) increase temp- more kinetic energy allows for more excited particles resulting in more solute particles colliding with solvent.
2) stir/ mix - increases particle contact resulting in a lesser time to dissolve.
3) crush substance to increase surface area. more surface area allows for more contact with the solvent.
Define polar molecule
A molecule in which one side of the molecule is slightly positive, and the another side is slightly negative.
Using this equation: M= n/L
How many grams of NaCl are needed to create a 15.0 Molar solution in 20.0 L of water?
15.0 M = n/ 20.0 L
n= 3.00 x 10 2 moles needed
3.00 x 102 moles x ( 58.44 g NaCl / 1 mole NaCl )
= 17500 g NaCl
The molar heat of fusion for ethanol(C2H6O) is 4.93 KJ/ mol
How much heat (in KJ) is transferred when 10.0 g of ethanol is frozen from 0 degrees Celsius as a liquid to 0 degrees Celsus as a solid
10.0 g ethanol x ( 1 mole ethanol/ 46.082 g ethanol) x ( -4.93 Kj/ 1 mole )
-1.07 KJ
The molar heat of vaporization for water is 40.7 KJ/ mol. Liquid water has a specific heat capacity of 4.184 joules per gram x celsius. Water vapor has a specific heat capacity of 1.996 joules per gram x celsius.
How much heat is required ( in joules) to heat 50.0 grams of liquid water from 50.0 Celsius to 120.0 Celsius?
( hint: break it into three steps )
1) Heat needed to heat 50.0 g H2O from 50 celsius to its boiling point (100 celsius)
q= 50.0 g ( 4.184 J/g x C ) 50.0 Celcius
q= 10460 J = 1.05 x 104 J
2) Heat needed for 50.0 g H2O to undergo vaporization
50.0 g H2O x ( 1 mole H2O / 18.0 g) ( 40.7 kj/ 1 mole ) x ( 1000 J / 1 KJ )
= 113,055.6 Joules = 1.13 x 105 joules
3) Hear required for 50.0 g H2O at 100 celsius to increase to 120.0 celsius
q= 50.0 g ( 1.996 j / g x C ) 20.0 Celsius
q= 1996 J = 2.00 x 103 J
So .. 10500 J + 113,000 J + 2000 J = 126,000 Joules