Acids, Bases, and Salts
Monoprotic
Has one ionizable hydrogen
Triprotic
Has three ionizable hydrogens
Diprotic
Has two ionizable hydrogens
What is the pH of a solution with [H-]= 1x10^-3 M
-log(1x10^-3)= 3
What is the pOH of a solution if the [OH-]= 3.5x10^-2 M?
-log(3.5x10^-2) =1.46
What is the pH of a solution if the [H+]= 7.2x10^-9 M
-log(7.2x10^-9) =8.14
Steps of a neutralization reaction
1. A measured volume of an acid solution of unknown concentration is added to a flask 2. Several drops of the indicator are added to the solution while the flask is gently swirled 3. Measured volumes of a base of known concentration are mixed into the acid until the indicator changes color
How do you read and determine the pH of a solution with the numbers?
1. A pH of less then 7 is acidic 2. A pH equal to 7 is neutral 3. A pH greater then 7 is basic
Buffer Solutions
1. A solution that is capable of resisting large changes in pH when relatively small amounts of acid or base are added 2. A solution of a weak acid and one of its salts or a solution of a weak base and one of its salts 3. Are available commercially
Properties of Acids
1. Giving food a sour taste 2. Forming solutions that conduct electricity 3. Causing indicators to change color
Finding the moles needed for neutralization 1. The term neutralization is used to describe both the reaction and the point at which a neutralization reaction is complete. How many moles of sulfuric acid are required to neutralize 0.5 mol of sodium hydroxide. The equation for the reaction is H2SO4 + 2NaOH------>Na2SO4 + 2H2O
1. Step one-Use the given amount of moles that need to be neutralized 2. Use the mole ratio of the substance you are looking for to neutralize the original mole amount (in this example it is the mole ratio between sulfuric acid and sodium hydroxide) 3. Set up equation (make sure you can cross cancel things out) 4. Multiply across to get the amount of moles it takes to neutralize the substance given
Properties of Bases
1. Tasting bitter 2. Feeling slippery 3. Changing the color of an indicator
Neutral
1.0 x 10^-7 M
A solution has a pOH of 12.4. What is the pH of this solution?
14-12.4= 1.6
What is the pOH of a solution that has a pH of 3.4?
14-3.4=10.6
Match each solution with its correct discription
18 M H2SO4- concentrated, strong acid 0.5 M NaOH- dilute, strong base 15 M NH3- concentrated, weak base 0.1 M HC2H302- dilute, weak acid 0.1 M HCl- dilute, strong acid
A solution has a hydrogen ion concentration of 1x10^-6 M. What is its pH?
6
What is the pOH of a neutral solution?
7
A buffer is a solution of a _______ acid and one of its salts, or a solution of _______ weak base and one of its salts.
A buffer is a solution of a WEAK acid and one of its salts, or a solution of WEAK base and one of its salts
If [H+] is written in scientific notation but its coefficient is not one, what do you need to calculate pH?
A calculator with the log function key
Indicator
A compound that changes color in the presence of an acid or base
What type of conjugate is the particle which remains when an acid has donated a hydrogen ion?
A conjugate BASE is the particle that remains when an acid has donated a hydrogen ion
Conjugate Acid
A conjugate acid is the ion or molecule formed when a base gains a hydrogen ion. For example NH4+ is the conjugate acid of NH3
Conjugate Acid-Base Pair
A conjugate acid-base pair consists of two ions or molecules related by the loss or gain of one hydrogen ion
Conjugate Base
A conjugate base is the ion or molecule that remains after an acid loses a hydrogen ion. For example, OH- is the conjugate base of the acid H20
What is a conjugate acid-base pair?
A conjugate base pair are two substances related by the loss or gain of a single hydrogen ion
When is a solution neutral?
A neutral solution is created when [H+]=[OH-]
What is a salt?
A salt is an ionic compound formed from the positive ion of the base and the negative ion of the acid
Weak Acid
A weak acid ionizes only slightly in aqueous solutions (Equation can be reversed. Double sided arrow)
Calculate the pH of each solution A. [H+]= 1x10^-5 B. [H+]= 4.4x10^-11 C. [OH-]= 2.2x10^-7 D. pOH= 1.4
A. -log(1x10^-5)= 5- acidic B. -log(4.4x10^-11)= 10.36- basic C. -log(2.2x10^-7)= 6.66---- 14-6.66=7.34- basic D. 14-1.4= 12.6- basic
Classify each solution as basic, acidic, or neutral A. [H+] =2.5x10^-9 M B. pOH =12.0 C. [OH-] =9.8x10^-11 M D. [H+] =1x10^-7 E. pH =0.8
A. -log(2.5x10^-9) =8.6- basic B. 12.0- basic C. -log(9.8x10^-11) =10- basic D. -log(1x10^-7) =7- neutral E. 0.8- acidic
Acid-Base Theory
Acids and bases can be classified in terms of hydrogen ions or hydroxide ions, or in terms of electron pairs
Bronsted-Lowry Acids and Bases
Acids are hydrogen donors while bases are hydrogen acceptors
Alkali metals react with water to form what type of solution?
Alkali metals react with water to produce basic solutions
A substance that can act both as an acid or base is said to be what?
Amphoteric
An ________ solution is one in which [H+] is greater than [OH-]. A _______ solution is one in which [OH-] is greater than [H+]
An ACIDIC solution is one in which [H+] is greater than [OH-]. A BASIC solution is one in which [OH-] is greater than [H+]
What is used to determine the equivalence point of a titration?
An acid-base indicator is used to determine the equivalence point of a titration
What can an acid-base indicator measure?
An acid-base indicator will change color over a small range of pH
What is an alkaline solution like?
An alkaline solution is basic and has a higher concentration of hydroxide ions
What allows for the most accurate measurement of pH?
An electronic pH meter gives a more accurate measurement
Hydronium
An ion that forms when a water molecule gains a hydrogen ion
What are bases?
Bases are compounds that react with acids to form water and a salt
Describe some distinctive properties of bases
Bitter, slippery, caustic, and conduct electricity
Bronsted-Lowry Continuation From Arrhenius
Bronsted-Lowry acids and bases include all the Arrhenius acids and bases plus additional substances that accept or donate hydrogen ions
Capacity of a Buffer
Buffer solutions have their limits. As acid is added to an ethanoate buffer, eventually no more ethanoate ions will be present to accept the hydrogen ions. At that point, the buffer can no longer control the pH
What is the purpose of titration?
By using careful measurements and calculations, the concentration of the unknown can be determined
Amphoteric Compound
Can be either a Bronsted-Lowry acid or base, such as water
Arrhenius Acids and Bases
Compounds are classified as Arrhenius acids or bases based on whether they ionize to yield hydrogen or hydroxide ions
Pairing of Conjugate Acids ad Bases
Conjugate acids are always paired with a base, and conjugate bases are always paired with an acid
Arrhenius Acids
Contain a hydrogen atom that is released in water to form a hydronium ion (H3O+)
Arrhenius Bases
Contain a hydroxide group which is released in water to form a hydroxide ion (OH-)
To go from a given pH to a concentration of [H+] use an antilog
Example. pH is 6.35 10^-6.35=4.46......E-7 [H+]= 4.5x10^-7
(True or false) Most pH values are whole numbers
False
(True or false) Some of the acids and bases included in the Arrhenius theory are not acids and bases according to the Bronsted-Lowry theory
False
(True or false) Al compounds that contain hydrogen are acids
False- Not all compounds that contain hydrogen are acids
In what form should you express the hydrogen ion concentration?
For pH calculations, the hydrogen ion concentration should be written in scientific notation
Acid-Base Reactions
Generally, an acid reacts with a base to form a salt and water
Acidic
Greater than 1.0 x 10^-7 M
Identify the hydrogen ion donor(s) and hydrogen ion acceptor(s) for ionization of H2SO4 in water.
H2SO4 (acid) + H2O (base) ---->HSO4- (conjugate base) + H3O+ (conjugate acid)
Identify all of the ions that may be formed when H3PO4 ionizes in water
H3PO4+H2O-----> H2PO4- + HPO4-2 + PO4-3 +H3O+
Common strong acids
HCl, HBr, HI, H2SO4, HNO3, HClO3, HClO4
What is hydrogen joined to?
Hydrogen is joined to a very electronegative element in a very polar bond
What does a water molecule that gains a hydrogen ion become?
Hydronium (H3O+)
What does a water molecule that loses a hydrogen ion become?
Hydroxide (OH-)
What makes a neutral solution?
If the concentration of hydrogen ions is equal to the concentration of hydroxide ions, the solution is neutral
What makes an acidic solution?
If the concentration of hydrogen ions is greater than the concentration of hydroxide ions, the solution is acidic
What makes a basic solution?
If the concentration of hydroxide ions is greater than the concentration of hydrogen ions, the solution is basic
Neutralization Reactions
In a neutralization reaction, a strong acid and strong base produce a neutral solution
Conjugate Acids and Bases
In essence, the reversible reaction of ammonia and water has two acids and two bases
Strong Acid
In general, a strong acid is completely ionized in aqueous solution (only goes one way. Arrow can only point in one direction)
In general, reactions in which an acid and a base react in an aqueous solution to produce a salt and water called ________ reactions.
In general, reactions in which an acid and a base react in an aqueous solution to produce a salt and water called NEUTRALIZATION reactions.
In water or aqueous solutions,_______are always joined to _______________as hydronium ions.
In water or aqueous solutions, HYDROGEN (H+) are always joined to WATER MOLECULES as hydronium ions.
Basic
Less then 1.0 x 10^-7 M
How are [H+] and [OH-] related in an aqueous solution?
Molarity
Self Ionization of Water
Molecules are in constant motion Enough energy to collide and form ions Only to a very small extent Reversible For example, H20<---->H+ + OH-
Common strong bases
NaOH, KOH, Mg(OH)2, Ca(OH)2, Sr(OH)2
When does neutralization occur?
Neutralization occurs when the number of moles of hydrogen ions is equal to the number or moles of hydroxide ions
How can you determine the concentration of an acid or base in a solution?
Neutralize the solution by doing a titration
Making a buffer
Prepared by mixing a weak acid or weak base with a salt of the acid or base
Salts are compounds consisting of an _______ from an acid and a _________ from a base.
Salts are compounds consisting of an ANION from an acid and a CATION from a base.
What are buffers?
Solutions in which the pH remains relatively constant when small amounts of acid or base are added
Describe some distinctive properties of acids
Sour and conduct electricity
Strong acids are __________ ionized in aqueous solution; weak acids ionize _________ in aqueous solutions.
Strong acids are COMPLETELY ionized in aqueous solution; weak acids ionize ONLY PARTIALLY in aqueous solutions.
Rank 1M of these compounds in order of increasing hydrogen ion concentration: weak acid, strong acid, strong base, weak base
Strong base, weak base, weak acid, strong base
How does the Bronsted-Lowry theory define acids and bases?
The Bronsted-Lowry theory defines acids as hydrogen (H+) donors and bases as hydrogen (H+) acceptors
Acid and Base Dissociation Constants
The acid and base dissociation constants Ka and Kb are measures of the strength of an acid or base
Buffer Capacity
The buffer capacity is the amount of acid or base that can be added to a buffer solution before a significant change in pH occurs
The pH Concept
The concentration of hydrogen ions is commonly expressed on the pH scale, which runs from 0-14
What factor is used to classify acids as strong or weak?
The degree to which they dissociate or ionize in water
What is the ion product constant for water (Kw)? Give the definition, the expression, and the value.
The ion product constant is the product of the H+ concentration and the OH- concentration. Kw=[H+] x [OH-]= 1.0x10^-14
What is the mathematical expression of pH?
The mathematical expression of pH is... pH=-log[H+]
Measuring pH
The pH of a solution can be measured with either a chemical acid-base indicator or with an electronic pH meter
Titration
The pH of an acid or base can be determined by running a titration
What is the pOH of a solution?
The pOH of a solution is the negative logarithm of the HYDROXIDE ION concentration
Equivalence Point
The point at which neutralization occurs is called the equivalence point
End Point
The point at which the indicator changes color is the end point of the titration
Describe how a buffer works to keep pH in a narrow range
The presence of the weak acid and salt acts like a "sponge" to soak up excess/additional hydrogen ions or hydroxide ions if an acid or base are added to the solution
The process of adding a known amount of solution of known concentration to determine the concentration of another solution is called _________.
The process of adding a known amount of solution of known concentration to determine the concentration of another solution is called TITRATION.
What is the reaction called in which water molecules produce ions?
The reaction in which water molecules produce ions is called the SELF-IONIZATION of water
Neutralization between HCl and NaOH
The salt that is formed from the neutralization of HCl and NaOH is NaCl, which is most commonly known as table salt
What is the name of the solution of known concentration?
The solution of known concentration is the standard solution
Strong and Weak Acids and Bases
The strength of acids and bases depends on the degree to which they ionize
Strengths of Acids and Bases
The strength of acids and bases is determined by the degree to which they ionize in a water solution
Conjugates
The transfer of a hydrogen ion from one compound to another creates two conjugate acid-base pairs
The words concentrated and dilute indicate how much acid or base is __________ in solution.
The words concentrated and dilute indicate how much acid or base is DISSOLVED in solution.
Concentrated and Dilute
The words concentrated and dilute indicate how much of an acid or base is dissolved in solution
Strong and Weak
The words strong and weak refer to the extent of ionization or dissociation of an acid or base
How do concentrated basic solutions differ from other basic solutions?
They are extremely caustic. They cause chemical burns to animal tissue
Why are acid-base reactions called neutralization reactions?
They neutralize each other. Complete reaction. Neither acidic or basic
Why is there a minus sign in the definition of pH?
To correct for log function resulting in a negative number
Determining Acid or Base
To determine whether a substance is an acid or a base, count the hydrogen on each substance before and after the reaction. If the number of hydrogen has decreased, that substance is the acid (donates hydrogen). If the number of hydrogen has increased, that substance is the base (proton acceptor)
(True or false) A conjugate acid is the particle formed when a base gains a hydrogen (H+) ion
True
(True or false) Acids react with compounds containing hydroxide ions to form water and a salt.
True
(True or false) Any aqueous solution in which [H+] and [OH-] are equal is described as a neutral solution
True
(True or false) The buffer capacity is the amount of acid or base that can be added to a buffer solution before a significant change in pH occurs.
True
(True or false) The words strong and weak refer to the extent of ionization or dissociation of an acid or base.
True
(True or false) You can calculate the hydrogen ion concentration of a solution if you know the pH
True
A 12.4 mL of a H2SO4 is completely neutralized by 19.8 mL of 0.0100 M Ca(OH)2. What is the concentration of the H2SO4 solution?
V1xM1=V2xM2 12.4 mL x M1= 19.8 ml x 0.01M 12.4 M1 = .198 M1= 0.198/12.4 M1=0.016 M
Titration Equation
VaNa=VbNb
What does the reaction of an acid with a base produce?
Water and a salt
In a reaction with HCl, is water an acid or a base?
Water is acting as a base because it is accepting a proton from the HCl
Hydrogen Ions From Water
Water self-ionizes into equal numbers of H+ and OH- ions
Hydrogen Ions and Acidity
Water-based solution may be acidic, basic, or neutral depending on the concentration of hydrogen ions present
Weak bases react with water to form the hydroxide ion and the _____________ of the base.
Weak bases react with water to form the hydroxide ion and the CONJUGATE ACID of the base.
When is a neutralization reaction complete?
When a solution contains equal numbers of hydrogen ions [H+] and hydroxide ions [OH-]
In aqueous solutions, what is the ion product constant for water?
[H+] x [OH-] = 1.0 x 10^-14 M =Kw
The _____ of a solution is the negative logarithm of the hydrogen ion concentration
pH
Acidic pH
pH<7.0
Neutral pH
pH=7.0
Basic pH
pH>7.0