Chemistry Regents Page 1 of 10Mr. Markic

Chapter 15 - Water and Aqueous Systems

This creates:

Surface Tension• The ___________force, or pull, that tends to minimize the surface area of the liquid

Surfactant• Any substance that ______________ with the ___________bonding _________water molecules

• __________________ surface tension

• Examples:

Vapor Pressure• Is the result of molecules ___________from the surface of the liquid and entering the vapor phase

Water in the Solid State• Ice is ________ dense than water

• Structure of ice is a regular open framework

Homogeneous Aqueous Systems• Aqueous Solution – water that contains _________________substances

• Solvent – the ________________medium (__________)

• Salt is the ___________ (gets ___________or ___________in the water)

• NaCl (__) + H2O (__) → NaCl (___)

Electrolytes

Chemistry Regents Page 2 of 10Mr. Markic• A compound that __________________ electric current when in _______________solution or in the

_____________state

• All ionic compounds are __________________ because they

__________________ into ions

• Strong electrolytes – compounds dissociate ________________as separate

ions

• Weak electrolytes – conducts electricity poorly because ions/molecules

__________________________ completely

Nonelectrolyte• A compound that does _______ conduct an electric current in wither aqueous solution or molten state

• Examples:

Sample ExerciseWhich of the following substances dissolve appreciably in water?

• HCl

• NH3

• CH4

• NaI

• MgSO4

• CaCO3

Decide which compounds are more likely to dissolve in water and which are more likely to dissolve in gasoline

a. CCl4

b. Na2SO4

c. Methane (CH4)

d. KCl

Sample ExerciseCalculate the percent by mass of water in washing soda, sodium carbonate decahydrate (Na2CO3 10H2O)

Practice ProblemsWhat is the percent by mass of water in CuSO45H2O?

Calculate the percent by mass of water in calcium chloride hexahydrate (CaCl26H2O)?

Chemistry Regents Page 3 of 10Mr. Markic

Write equations to show how these substances ionize or dissociate in water

a. NH4Cl

b. Cu(NO3)2

c. HC2H3O2

d. BaCl2

Chapter 16 - Solutions

Solution Formation• How quickly the solute dissolves in a solvent• Rate can be increased by increasing:

1.

2.

3.

1. ____________________

• __________________ the solute increases the chance for the solvent to react and form a solution

2. ____________________

• At high temperatures, the ______________ energy of molecules is greater than at lower temperatures

• The more rapid motion of molecules leads to an increase in ________________ and ___________ in

________________ between molecules

3. ____________________________

• Increasing the surface area of a solute increases the chances for a reaction

____________________• Is the amount of substance that dissolves in a given quantity of a solvent at a given temperature to

produce a __________________ solution

• ________________ + _________________ ® ____________________

• Ex: NaCl(s)(solute) + water(l)(solvent) ® NaCl(aq) (solution)• Saturated solution – contains the ___________________ amount of solvent at constant temperature

Chemistry Regents Page 4 of 10Mr. Markic• Unsaturated – a solution that contains ___________ solute than a saturated solution

• Miscible – two liquids that ____________________ in each other

• Immiscible – liquids that are __________________ in one another

Factors Affecting Solubility1. ________________________ • Affects the solubility of ___________, _______________, and ______________ solutes in a solvent

2. ______________________ • Affects only the solubility of ________________ solutes

1. Temperature• Table _________________________

• The solubility of most solid substances __________________ as temperature _________________

(__________________)

• Gases are ___________ soluble in liquids when temperatures are _____________ (_______________)

• Supersaturated solution – contains more _______________ that it can theoretically hold at a given

temperature

Sample ExerciseAt what temperature will the solubility of KNO3 be 50 g/per 100g of H2O? At 100 g of KNO3?

How much KClO3 is needed to saturate 50 g of H2O at 90°C?

How many grams of NaNO3 will precipitate if a saturated solution of NaNO3 in 200g H2O at 50°C is cooled to 20°C?

The solubility of KCl in water is 34.0 g KCl/100g H2O at 20°C. A warm solution containing 50.0 g KCl in 100 g H2O is cooled from 75°C to 20°C.

a. How many grams of KCl remain dissolved? b. How many grams came out of solution?

A solution contains 70 grams/100 g H2O at 60°C. Determine if the solution is unsaturated, saturated, or unsaturated for: KI, NaNO3, HCl, KNO3

Chemistry Regents Page 5 of 10Mr. Markic

Which solution has the highest solubility in 100 g of H2O at 40°C?

A solution contains 14 g of KCl in 100 g of water at 40°C. What is the minimum amount of KCl that must be added to make this a saturated solution?

How many grams of the compound KCl must be dissolved in 200 g of water to make a saturated solution at 60°C

Which amount of the compound dissolved in 100 g of water at the stated temperature represents a solution that is saturated?

(1) 20 g KClO3 at 80°C(2) 40 g KNO3 at 25°C(3) 40 g KCl at 60°C(4) 60 g NaNO3 at 40°C

2. Pressure• Increasing pressure prevents ______________________

• Increasing pressure makes gaseous molecules _____________ soluble in liquid form

Concentrations of Solutions• Molarity (M) - The number of moles of a solute dissolved in 1L of solution

• Also known as _____________________________

• Molarity (M) = molesof soluteliters of solution

• Table T

• Dilute Solution – one that contains a _______________ amount of solute

• Concentrated Solution – contains a ________________ amount of solute

Sample Problem

Chemistry Regents Page 6 of 10Mr. MarkicHousehold laundry bleach is a dilute aqueous solution of sodium hypochlorite (NaClO). How many moles of solute are present in 1.5 L of 0.70 M NaClO?

Practice ProblemsHow many moles of ammonium nitrate are in 335 mL of 0425 M NH4NO3?

How many moles of solute are in 250 mL of 2.0 M CaCl2? How many grams of CaCl2 is this?

A saline solution contains 0.90g of NaCl per 100.0 mL of solution. What is its molarity?

How many grams of solute are present in 1.5 L of 0.20M Na2SO4?

Making Dilutions• Making a solution ____________ concentrated by ________________ it with more solvent• M1 x V1 = M2 x V2

• Volumes can be in liters or in milliliters as long as the same units are used for both V1 and V2

Sample ProblemHow many milliliters of aqueous 2.00 M MgSO4 solution must be diluted with water to prepare 100.0 mL of aqueous 0.400 M MgSO4?

Sample Exercise

Chemistry Regents Page 7 of 10Mr. MarkicHow many milliliters of a solution of 4.00 M KI are needed to prepare 250.0 mL of 0.760 M KI?

How could you prepare 250 mL of 0.20 M NaCl using only a solution of 1.0 M NaCl and water?

Parts per Million (Table T)• Ratio between mass of solute and total mass of solution

• Useful for very ___________ solutions

• Table T

parts per million = gramsof solutegrams per solution x 1 000 000

Carbon dioxide gas has a solubility of 0.972 g/ 100 g of H2O at 40°C, express this in parts per million.

Approximately 0.0043g of oxygen can be dissolved in 100.0g of water at 20oC. Express this in terms of parts per million.

Colligative property -• A property that depends on the __________________ of solute particles, _______ their identity • Three important examples in solutions:

o __________________________________

o __________________________________

o __________________________________

Chemistry Regents Page 8 of 10Mr. Markic1. Vapor-Pressure Lowering

a measure of the force exerted by a gas ______________ a liquid Solutions with nonvolatile (not easily ___________________) solutes have _____________ vapor

pressures than pure solventso E.x. Salt water has a lower vapor

pressure than pure water

Water forms a “__________” around dissolved particles

This leaves fewer water molecules with enough KE to escape as vapor

The decrease in a solution’s vapor pressure is proportional to the ______________ of particles the solute makes in a solution

E.x. NaCl is 2x as effective as glucose, CaCl2 is 3x as effective as glucose

2. Freezing-Point Depression ____________________ in temperature between the freezing point of a solution and the freezing

point of the pure solvent Solutions have _______________ freezing-points than pure solvents The presence of a solute disrupts the formation of the orderly pattern found in a solid Therefore, _________________ KE must be removed before the solution can freeze The magnitude of the freezing-point depression is _________________ to the number of solute

particles dissolved in the solvento Why would CaCl2 be better than NaCl for melting ice?

3. Boiling-Point Elevation• The difference in temperature between the boiling point of a solution and the boiling point of the pure

solvent• Boiling Point – is the temperature at which the vapor pressure of the liquid phase _______________

the atmospheric pressure• Solutions have _______________ boiling-points than pure solvents • Recall… _______________________________________________________• Therefore, it takes _______________ KE for the solvent

particles to overcome the attractive forces that keep them in the liquid

• The magnitude of the boiling-point elevation is _______________________ to the number of solute particles dissolved in the solvent

Chemistry Regents Page 9 of 10Mr. Markic

Sample Exercise• An equal number of moles of KI and MgF2 are dissolved in equal volumes of water. Which solutions

has the higher:

1. Boiling point 2. Vapor pressure 3. Freezing point

• Why is salt (NaCl) put on icy roads and sidewalks in the winter?

Assume equal aqueous concentrations of each of the following substances. Which has the lowest freezing point?

(1) C2H22O6

(2) CH3OH

(3) C12H22O11

(4) NaOH

Which solution has the highest boiling point?

(1) 1.0 M KNO3

(2) 2.0 M KNO3

(3) 1.0 M Ca(NO3)2

(4) 2.0 M Ca(NO3)2

Which solution has the highest boiling point?

a) seawater b) 1.0M KNO3 or c) 0.100M KCl or

How does the freezing point of a 1.5M solution of potassium nitrate compare to a 1.5M solution of sodium nitrate?

Vapor Pressure & Boiling Liquids are held together by _____________________________ Some particles at the surface of the liquid have sufficient energy to escape & enter the gaseous phase

o __________________________ Vapor pressure = the _________________ that these gaseous particles exert _____ the liquid below What will happen to the vapor pressure as the temperature is increased?

As temperature _________, vapor pressure __________ At some point the vapor pressure ________ atmospheric pressureo Gases vaporize not only at the surface, but also within the liquid (_______________)

Chemistry Regents Page 10 of 10Mr. Markic

o This is the boiling point -• What is the vapor pressure of water at 105°C?

• What is the vapor pressure for a sample of ethanoic acid at 100°C?

• Which of the substances on Table H has the greatest intermolecular forces of attraction between molecules?

• Which of the substances on Table H has the weakest intermolecular forces of attraction?

• What is the normal boiling point for water?

• What is the vapor pressure of water at its normal boiling point?

• At what temperature will water boil at a pressure of 30 kPa?

• At what temperature will water boil at a pressure of 145 kPa?

• As the pressure on a liquid is changed from 100 kPa to 120 kPa, the temperature at which the liquid will boil will be?