Chemistry: Hood River Valley High School Name:_________________________________

Unit 9 Packet and Goals Period:_________

Unit 9 – Water, Solutions & Acid/Base Chemistry Unit Goals: As you work through this unit, you should be able to…

1. describe hydrogen bonding in water and how it explains water’s high surface tension, low vapor pressure, high specific heat, high boiling point, and high heat of vaporization.

2. describe a solution and its components, and why substances are soluble 3. distinguish among strong electrolyte, weak electrolyte, and nonelectrolyte solutions. 4. identify factors that determine the rate a solute dissolves. 5. understand and identify unsaturated, saturated and supersaturated solutions 6. solve concentration problems involving molarity, dilution, and percent. 7. understand how to distinguish between Arrhenius and Bronsted-Lowry acid and bases 8. understand how some compounds can function as both a Bronsted acid and a Bronsted base 9. understand how to identify conjugate acid-base pairs in a reaction 10. be able to calculate: concentrations of H3O

+, concentrations of OH

-, and pH of a solution

11. understand the concept of equilibrium using acids and bases 12. compare the strengths of acids and bases using their dissociation constants, Ka and Kb 13. use the pH and molarity of a weak acid solution to calculate Ka

Readings:

Chapters 15.1-15.2 (pp 445-453), 16.1-16.2 (pp 471-486), and 19.1-19.3 (pp 587-611)

Assignments: Classwork and Labs

Description/Goals 5 4 0

A 1 Ch 15 Reading Guide Goals: 1 – 3

Unit 9 Assignment Packet

A2

Ch 16 Reading Guide Goals: 4 – 6

Solubility of a Salt Activity

A3

Concentration Problems Goals: 5-6

Solubility Curve Lab

A4

Ch 19 Reading Guide Goals: 7 – 13

Making a Solution & Dilution Lab

A5

pH, pOH calculations Goals: 7-11

Acid/Base Lab

A6

Unit 9 Exam OR Final Exam

A7

Unit 9 - Water, Solutions & Acid/Base Chemistry Notes

15.1 Water and its Properties

Draw a picture of the water molecule below. Label the slightly positive atom and the slightly negative atom

in your drawing.

In general, polar molecules are attracted to one another. Draw 5 water molecules in a picture and showing

how they would align themselves.

Hydrogen Bonding in Water

• Water exhibits _____________________ between molecules. What is meant by “hydrogen

bonding”? Hydrogen bonding is the ________________ that exists between a region of slight

______________ from one molecule to a region of slight ______________ on a ______________

molecule. It is not a __________bond, but more of an attraction based on opposite charges.

• Many unique and important properties of water result from hydrogen bonding. List 5 characteristics

of water here that can be accounted for by hydrogen bonding.

• What is surface tension? The inward __________or _______________that tends to stick particles to

each other at the ______________of the liquid. It is like a tough “skin” on the surface of water. It is

explained by water’s ability to form _______________bonds.

• Draw how surface tension works below

Magic of Ice

• A “typical” liquid _____________while it is cooling… explain this statement using the kinetic

molecular theory. Cooler particles move __________than ___________particles. Therefore, cooler

particles are ___________together and more _________.

• Therefore, what would happen to the density of the substance as it changes from liquid to solid?

They would normally __________.

For example. Lead shot _______ in molten (liquid) lead.

• Digram how water’s density changes as it cools and warms in lakes while they move through 4

seasons:

• What temperature does water have a maximum density?

• Why does ice float on liquid water?

• Why does ice behave so differently? Draw the alignment of water molecules as ice forms, using

figure 17.9 from page 481 as your guide.

• The fact that ice floats has important consequences for life on earth. Describe at least 3 reasons

why.

15.2 Homogeneous Aqueous Solutions

Aqueous Solutions

• Solution – a homogeous___________consisting of a ___________and a ___________

• Solute – ___________particles

• Solvent – ___________medium

• Aqueous Solution – solution in which the ___________is ___________

Solvation

• Process by which a ___________dissolves

• Solvent has to be ___________to ___________for solvation to occur (figure 15.8 – page 445)

• If solute is more ___________to ___________rather than the ___________, solvation will not occur

and the solute is said to be _____________

• “________dissolves ________” is a good rule of thumb to tell whether or not a solute will dissolve in

a solvent, in other words solutes and solvents with similar ___________will make a solution

• δ+ H ___________Cl- ions

• δ- O ___________Na+ ions

• A similar scheme can be used to illustrate the dissolution of a molecular substance in water.

• “Like dissolves like”

Solution Types

Solutions can be any type of matter (_______,________,_______) interaction

Miscible:

– When 2 _______form a solution they are said to be _______.

Liquid/Liquid solutions don’t really have a _______and _______

They can _______in each other in any amount.

These make ______________mixtures

Examples:

Water and _______

_______and Alcohol

Immiscible:

– When 2 liquids _________ form a solution. NOT _______

Ex. Water and _____

– These make ______________mixtures

Alloy:

– Solution of 2 or more ______________

Aqueous: Solution with _________as the Solvent

Electrolyte

• Compound that will _________an __________current in __________solution or the ________state

• _________compounds are electrolytes because they have a __________and __________charges

that can conduct an electric current

• Electrolytes can be classified as __________or __________depending on the extent to which the ions

__________in solution

• Non-electrolyte

– Compound that will not conduct electricity in aqueous solution or the molten state

– Many molecular compounds are non-electrolytes (compounds of carbon especially)

• Example of dissociation of strong electrolyte: NaCl

16.1 Properties of Solutions

Factors Affecting Solution Formation

• __________– increases ________of contact between solvent and solute

• Increase in __________– increases __________energy, leading to an increase in the rate of _______

between __________and __________

• Increase in ________ _______– increases the __________contact between solvent and solute

Solubility

• Amount of __________that can be __________in a __________of solvent at a given ____________

• If a ________solute can be dissolved in a __________solvent then the solute is __________, if it can’t

be dissolved the solute is __________

• Solubility represents a __________ __________

– Usually expressed as _____g solute/______ of Water.

– Is effected mostly by ____________in solid solutes

– Is effected by Temperature and __________in __________solutes.

• What is the solubility of sodium chloride at 25°C

Solutions

• _______________Solution – contains the __________amount of solute particles that can be

__________in a given __________of solvent at a constant temperature

• _________________Solution – contains ________ ________the __________amount of solute

particles that can be dissolved in a given quantity of solvent at a constant temperature

• _________________Solution – contains ________ ________the __________amount of solute

particles that can be dissolved in a given quantity of solvent at a constant temperature

– Difficult to create and Usually unstable.

– Not all Solute/Solvent Combinations can result in a Supersaturated Solution

Factors Affecting Solubility

• Solubility of a solid solute generally __________with temperature

– Examples:

• Solubility of a gaseous solute ___________with temperature, but ___________with ___________

– Increase in Temperature Decreases Solubility

– Examples:

– Increase in Pressure Increases Solubility

– Examples

16.2 Concentrations of Solutions

Concentration of Solutions

• The concentration of a solution is a measure of the amount of __________that is dissolved in a given

quantity of __________.

• ____________ _____________ – number of __________of __________that can be dissolved per

__________of __________ (in liters)

M =

• Units:

The volume is the TOTAL volume of the __________, NOT the volume of __________

Molarity Example

• What is the molarity of a 2.0 L solution containing 4.0 mol NaCl?

Sample Problems

1. A saline solution contains 0.9 grams of sodium chloride per 100 mL of solution. What is the molarity of

the solution?

2. A solution has a volume of 2.0 Liters and contains 36 grams of glucose. What is the molarity of the

solution? (Molar mass of glucose, C6H12O6 = 180 g/mol)

3. A solution has a volume of 250 mL and contains 0.7 mol of table salt. What is its molarity?

4. How many moles of solute are present in 1.5 L of 0.24 M Na2SO4?

5. How many moles of ammonium nitrate are in 335 mL of 0.425 M NH4NO3?

How many grams is this?

Making Dilutions

• Dilutions are used to make ________ concentrated solutions by increasing the _________of solvent.

• When making a dilution the number of ________of solute stays CONSTANT.

• Moles of solute = molarity (M) x liters of solution (V)

– Example. How many moles of NaCl are in 10L of a 2M solution?

• Formula for making a dilution:

Dilution Example

• How many milliliters of 5.0 M CuSO4 would be needed to prepare 100.0 ml of 0.50 M CuSO4?

Diagram the process below the math and include the numbers in your diagram.

Example Problems:

1. How many milliliters of a stock solution of 2.0 M MgSO4 would you need to prepare 100 mL of 0.4 M

MgSO4?

2. How many milliliters of a stock solution of 4.0 M KI would you need to prepare 250 mL of a 0.76 M

KI?

3. How many moles of HCl must be added to make 2.0L of a 6.0 Molar Solution of HCl (aq)

4. Suppose you need 250 mL of a 0.2 M NaCl, but the only supply of sodium chloride you have is a

solution of 1.0 M NaCl. How do you prepare the required solution? (diagram & describe the exact

process)

5. What is the molarity of a solution if enough water is added to 35g of KNO3 to make 550mL of

solution?

6. How much water must to added to 250mL of 2.0 M KCl to produce 0.75 M KCl?

Percent Solution

• % by _________: Used only in ________/Liquid Solutions

%(v/v) = volume ___________/ volume ___________

» Units: ___________must be in same ________

• % by ________: Used in ____________Solutions

%(m/v) = mass solute / volume solution

» Units__________

Percent Volume Example

– What is the percent volume of acetone in water if 25 ml of acetone is added to 75 ml of water?

Percent Mass Example

– What is the % (m/v) of a 100 ml aqueous solution containing 10 g of NaCl?

Example Problems

1. What is the percent by volume of ethanol in the final solution when 85 mL of ethanol is diluted to a

volume of 250 mL with water?

2. If 100 mL of pure acetone is diluted with water to a total solution volume of 200 mL, what is the

percent by volume of acetone in the solution?

3. How many grams of glucose would you need to prepare 2 Liters of 2.8% glucose (m/v) solution?

4. Calculate the Molarity if 25.0g of NaCl is dissolved in enough water to make 750mL of NaCl (aq)

5. Calculate the %Mass concentration of the solution above.

6. Calculate the %Volume when 25mL of Vinegar (C2H4O2) is mixed with 125mL of water

19.1 Describing Acids and Bases

Properties of Acids and Bases

Acids

– Have a ________taste

– Change the color of many __________

– Are _____________ (react with metals)

– _____________bases

– Conduct an __________current

Bases

– Have a ___________ taste

– Change the color of many ___________

– Have a ___________feeling

– Neutralize ________

– ____________an electric current

Define an Acid

_______________ containing compounds

Ionize to yield _____________ ions (______)

What is an example of: Monoprotic acid: Diprotic acid: Triprotic acid:

Define and Base

_______________ containing compounds

Ionize to yield _____________ ions (______) Show an Arrhenius Base Solvating in Water

– NaOH

– KOH

Only the _________________ in very _________

bonds are ______________

Compare

HCl -

CH4 –

HC2H3O2 –

Metals will react with _________

to form ____________

Example: Write the balanced equation for __________ metal reacting with __________

Bronsted-Lowry Acids and Bases:

One problem with the Arrhenius theory is that it is not ________________ enough:

We need a better definition to include more ______________that behave like acids and bases, yet

don’t start with “____” or end with “_____”

For example, NH3 (ammonia) and Na2CO3 (sodium carbonate) are ____________, yet don’t end with

hydroxide, OH- .

Define: Bronsted-Lowery Acids:

-

-

Define: Bronsted-Lowery Bases:

What are conjugates?

Conjugate Acid

-

-

Conjugate Base

-

-

Show ammonia reaction with water and label the conjugate acid-base pairs::

Show HCl reacting with water and label the conjugate acid-base pairs:

Define amphoteric:

Water is amphoteric:

Problems:

1. Which substance is amphoteric

a. H2CO3 b. H2PO4- c. HCl d. H2SO4

2. Determine whether the following acids are monoprotic, diprotic, or triprotic

a. H2CO3 b. H3PO4 c. HCl d. H2SO4

3. Write the equation for the ionization of nitric acid (HNO3) in water

Label the conjugate acid-base pairs

4. Write equation for the ionization of sulfuric acid (H2SO4) in water removing just one hydrogen. Label

the conjugate acid-base pairs.

5. Write the equation for the removal of the second hydrogen from the equation above: Label the

conjugate acid-base pairs.

Problem set 1: Write the conjugate acids for the following bases:

a. Cl-1

b. HS04 -1

c. NH3

Problem set 2: Write the conjugate bases for the following acids:

a. H2O c. HCO3 -1

b. H2CO3 d. H30 +1

19.2 Hydrogen Ions and Acidity

Hydrogen Ions From Water:

Occasionally, the collisions between water _________________are energetic enough that a

_________________ion is transferred from one _________________molecule to another.

Show the _______ _________________ of water reaction:

A water molecule that loses a hydrogen ion becomes a _________________(______)

A water molecule that gains a hydrogen ion becomes a _________________(______)

The self ionization of water occurs only to a small extent:

What is the concentration of the hydronium ion or hydroxide ion in pure water at 25 degrees C?

[H3O+] = _____________ and [OH-] = _______________

* the brackets stand for concentration in molarity units.

Why is water said to be neutral?

Because water produces ___________ amounts of _____ and ______ ions which recombine

to form ___________ again as _____________________ is established.

For aqueous solutions, the _________________of the _________________ion concentration and the

_________________ion concentration is known as the ion-product constant for water, ______.

Write the expression for Kw:

From this point forward H30+ and H+ are _________________!

In acidic solutions, the [H+] is ________________than the [OH-]. Therefore, the [H+] is greater than

_________________. In basic solutions, the [H+] is _____________than the [OH-].

What is another name for basic solutions? ____________________

Sample Problem 1

If [H+] = 1 x 10 -5 mol/L, is the solution acidic, basic, or neutral? What is the [OH-] of this solution?

Problem Set 3

Classify each solution as acidic, basic, or neutral:

a. [H+] = 6.0 x 10 –10 M

b. [OH-] = 3.0 x 10 –2 M

c. [H+] = 2.0 x 10 –7 M

d. [OH-] = 1.0 x 10 – 7

The pH Concept: Since the hydrogen ion concentration in moles per liter is inconvenient to use, a more widely used system,

called the pH scale, is used.

What is a pH scale and what do we use it for?

– The _________________ logarithm of the _________________-ion concentration

– A solution with a pH less than_________ is acidic

– A solution with a pH greater than _________ is basic

Write the formula for calculating pH:

Sketch in a pH scale, indicating where acids, bases, and neutral solutions fall. (page 656 is helpful here)

Sample Problem

What is the pH of a solution with a hydrogen-ion concentration of 4.2 x 10 -10 mol/L?

Problem Set 4

1 Determine the pH of the following solutions:

a. [H+] = 0.045 M

b. [H+] = 8.7 x 10 –6 M

c. [H+] = 0.0015 M

d. [H+] = 1.2 x 10 –3 M

2. What are the pH values of the following

solutions?

a. [H+] = 1.0 x 10-12 M

b. [H+] = 1.0 x 10 –4 M

Calculating [H+] from pH:

Rearrange the pH equation to solve for [H+]

Sample Problem 3

The pH of a solution is 6.35. What is the hydrogen ion concentration?

Problem Set 5

3. Calculate [H+] for each solution:

a. pH = 5.00

b. pH = 12.83

4. What are the hydrogen ion concentrations of:

c. pH = 4.00

d. pH = 11.55

Calculating pH from [OH-]

How do you calculate [H+] from [OH-]?

Sample Problem 4

What is the pH of a solution if the [OH-] = 4 x 10 -11 ?

Problem set 6

5. Calculate the pH for each solution:

a. [OH-] = 4.3 x 10 –5 M

b. [OH-] = 4.5 x 10 -11 M

6. Calculate the pH for each solution:

a. [OH-] = 5.0 x 10 –9 M

b. [OH-] = 8.3 x 10 –4 M