CHAPTER EIGHT: ACIDS AND BASES Flashcards
Describe what the term ACID means
It comes from the Latin word “acidus”, which means “sour”. Acidic foods have a sour taste.
ACIDS are substances that produce _____ ions when they dissolve in water. Because of this, they are also ___________.
hydrogen (H+)
electrolytes
It is the _______ ions that give acids a sour taste, change blue litmus indicator to red, and corrode some metals.
hydrogen
NAMING ACIDS:
When an acid dissolves in water to produce a hydrogen ion and a simple nonmetal anion, the prefix ____ is used before the name of the nonmetal, and its _____ ending is changed to “___ acid”.
Give an example using hydrogen chloride.
hydro
ide; ic acid
Example: hydrogen chloride (HCl) dissolves in water to form HCl (aq), which is named hydrochloric acid, HCN (aq).
NAMING ACIDS:
When an acid contains oxygen, it dissolves in water to produce a hydrogen ion and an oxygen-containing ____________ anion.
The most common form of an oxygen-containing acid has a name that ends with “___ acid”. The name of its polyatomic anion ends in ______.
polyatomic anion
ic acid
ate
NAMING ACIDS:
An acid that contains one less oxygen atom than the common form is named as an “____ acid”.
The name of its polyatomic anion ends with _____.
ous acid
ite
By learning the names of the most common acids, we can derive the names of the corresponding ous acids and their polyatomic anions. (Do you have to learn the whole chart?)
See Table 8.1 on page 287
What are BASES, according to the Arrhenius theory?
Arrhenius bases are also __________.
Give an example using sodium hydroxide
ionic compounds that dissociate into a metal ion and hydroxide ions (OH-) when they dissolve in water.
electrolytes
Example: sodium hydroxide is an Arrhenius base that dissociates in water to give sodium ions (Na+) and hydroxide ions (OH-).
Most Arrhenius bases are formed from Groups _____ and _____ metals. Give 4 examples.
1A (1) and 2A (2)
Examples: NaOH, KOH, LiOH, and Ca(OH)2
The ________ ions give Arrhenius bases common characteristics such as a bitter taste and soapy, slippery feel.
A base turns litmus indicator _______ and phenolphthalein indicator ______ (colors).
hydroxide ions (OH-)
blue; pink
Typical Arrhenius bases are named as __________. Give an example.
Hydroxides. LiOH= Lithium hydroxide
See chart on page 287 for more…
What is a Bronsted-Lowry ACID?
it donates a proton (hydrogen ion, H+) to another substance. Thus, a B-L acid is a proton (H+) DONOR.
What is a Bronsted-Lowry BASE?
It accepts a proton. Thus, a B-L base is a proton (H+) ACCEPTOR.
Does a free, dissociated proton (H+) actually exist in water? Why or why not?
What is a HYDRONIUM ION?
No, it does not. It undergoes hydration just like other cations because it has a strong attraction to polar water molecules.
The hydrated H+ is written as H3O+ and is called a HYDRONIUM ION.
We can write the formation of a hydrochloric acid solution as a transfer of a proton from _______ _______ to water.
By accepting a proton in the reaction, water is acting as a ______ according to the Bronsted-Lowry concept.
hydrogen chloride
base
see diagram on page 288
Ammonia (NH3) acts as a _______ by accepting a proton when it reacts with water.
Because the nitrogen of NH3 has a stronger attraction for a proton than the oxygen of water, water acts an an _____ and _____ a proton.
BASE
ACID; donates
see diagram on page 288
According to the Bronsted-Lowry theory, what is a CONJUGATE ACID-BASE PAIR?
Give an example using the acid HA
A conjugate acid-base pair consists of molecules or ions related by the loss or gain of one H+. Every acid-base reaction contains two conjugate acid-base pairs because protons are transferred in both the forward and the reverse reactions.
When the acid HA donates H+, the conjugate base A- forms.
When the base B accepts the H+, it forms the conjugate acid BH+.
See page 289- how to write this as a general equation for a B-L acid-base reaction, and how to identify the conjugate acid-base pairs in a reaction between hydrofluoric acid, HT and water. (+ another example on p. 290)
Substances that can act as both acids and bases are ______________.
_______ is the most common of these, and the acid or basic behavior depends on ______________________________.
amphoteric
…depends on whether the other reactant is a stronger acid or base.
The strength of an acid is determined by ______________________.
The strength of a base is determined by ______________________.
acid- the moles of H3O+ that are produced for each mole of acid that dissolves.
base- the moles of OH- that are produced for each mole of base that dissolves.
What is DISSOCIATION?
In the process called DISSOCIATION, an acid or base produces ions in water
How do strong acids and strong bases dissolve in water?
How do weak acids and weak bases dissolve in water?
Strong: dissociate completely in water
Weak: dissolve mostly as molecules with only a few dissociating into ions.
Strong acids are examples of strong electrolytes because _____________.
Give an example using HCl dissociating in water.
they donate protons so easily that their dissociation in water is virtually complete.
Example: when HCl, a strong acid, dissociates in water, H+ is transferred to H2): the resulting solution contains only the ions H3O+ and Cl-. We consider the reaction of HCl in H2O as going 100% to products.
The equation for the dissociation of a strong acid, such as HCl, is written with a single arrow to the products. See page 291.
There are only _____ common strong acids. All other acids are weak.
SIX
see Table 8.3 on page 292
WEAK ACIDS are weak electrolytes because ________________.
they produce only a few ions in water.
A solution of a strong acid contains all ions, whereas a solution of a weak acid contains mostly molecules and few ions.
A weak acid is written with a _____ arrow.
A longer reverse arrow may be used to indicate ___________________
double arrow (Ex: carbonic acid H2CO3)
…that a solution of the weak carbonic acid contains mostly undissociated acid molecules of the reactants and a few H3O+ and bicarbonate ions of the products.
See page 293
If HA is a strong acid in water, its aqueous solution consists of the ions _____ and ____.
If HA is a weak acid in water, its aqueous solution consists of mostly ________ and only a few _____ and ________ ions.
H3O+ and A-
undissociated HA and only a few H3O+ and A- ions.
See page 293 for the equations
A STRONG BASE is a strong electrolyte that dissociates completely in water to give an aqueous solution of a ____ ion and ____ ions.
metal; hydroxide
The Group 1A (1) hydroxides are _____ soluble in water, which can give high concentrations of _______ ions.
The Group 2A (2) bases are _____ soluble in water, but they are strong bases because they ______________ __________ as ions.
…very soluble in water; high concentrations of OH- ions.
…less soluble in water; dissociate completely as ions.
See example page 293
A WEAK BASE is an electrolyte that produces ________________ in solution.
only a few ions in solution.
IONIZATION of WATER:
* Water can be both an acid and a base.
- One water molecule acts as an acid by __________ to another water molecule, which acts as a base.
- Every time a _______ is transferred between two water molecules, the products are one _________ and one ______.
donating H+
H+
the products are one H3O+ and one OH-
from page 295-
IONIZATION OF WATER:
* In the equation for the ionization of water, there is both a _____ and a ____ direction???
forward; reverse
from page 295-
Experiments have determined that, in pure water, the concentrations of H3O+ and OH- at ????? degrees C are each ____________.
Square brackets are used to indicate the concentrations in _______????? per liter
1.0 x 10-^7 M.
?????? (M)
From page 295-
What is the ??????? PRODUCT CONSTANT OF WATER (Kw)
When the concentrations of H3O+ and OH- in water are multiplied, we obtain the expression and value call the ???? PRODUCT CONSTANT OF WATER (Kw), which is 1.0 x 10^-14. The concentration units are ???? in the Kw value.
See page 295 for the equations.
The Kw value is ______________ and applies to any aqueous solution at ___ degrees C because all aqueous solutions contain both H3O+ and OH-.
1.0 x 10^-14
25 degrees C
When is a solution considered NEUTRAL?
Are most solutions neutral?
When the [H3O+] and [OH-] in a solution are equal.
No; they have different concentrations of [H3O+] and [OH-]
If acid is added to water, there is an ______ in [H3O+] and a _____ in [OH-], which makes it an ACIDIC SOLUTION.
increase, decrease
If base is added to water, there is an _______ in [OH-] and a ________ in [H3O+], which makes it a BASIC SOLUTION.
increase, decrease
Thus, for any aqueous solution, whether it is neutral, acidic or basic…the product
[H3O+] [OH-] is equal to ___________.
Kw (1.0 x 10^-14).
See Table 8.4 on page 295
Many careers require the measurement of the [H3O+] and [OH-] of solutions.
On the pH scale, a number between 0 and 14 represents the _______ for most solutions.
A neutral solution has a pH of ______
An acidic solution has a pH ____ than ____
A basic solution has a pH ____ than ____
…represents the [H3O+] for most solutions
neutral- 7.0
acidic- less than 7.0
basic- greater than 7.0
What are 3 ways to determine the pH of a solution?
- a pH meter
- pH paper
- indicators that turn different colors corresponding to different pH values
The pH scale is a ________ scale that corresponds to the [H3O+] of aqueous solutions.
Mathematically, pH is the _______ ______ (base 10) of the [H3O+]
logarithmic scale
negative logarithm
pH= -log[H3O+]
pH scale:
- The negative powers of 10 in the molar concentrations are converted to ______ numbers.
- the number of DECIMAL PLACES in the pH value is the same as the number of _______ in the coefficient of __________.
- the number on the left of the decimal point in the pH value is the power of _____
- Because pH is a log scale, a change of one pH unit corresponds to a _____-fold change in [H3O+]
- it is important to note that the pH ______ as the [H3O+] increases.
- positive (see page 299)
- significant figures in the coefficient of [H3O+]
- power of 10
- 10-fold change
- decreases
Calculating the [H3O+] from pH:
- this is a reverse of the pH calculation.
- for whole number pH values, the negative pH value is the _________ in the [H3O+]
concentration. - for pH values that are NOT whole numbers, the calculation requires the us of the _____ key.
power of 10
[H3O+] = 1 x 10^-pH
- 10^x key See page 301 for instructions
See Table 8.5 for a comparison of [H3O+] , [OH-], and their corresponding pH values
on page 302
What is a SALT?
an ionic compound that does not have H+ as the cation or OH- as the anion
Acids react with certain metals to produce a _____ and ________ gas.
Metals that react with acids include which 8 metals?
In reactions that are SINGLE REPLACEMENT REACTIONS, the _____ ion replaces the ______ in the acid.
salt; hydrogen gas
potassium, sodium, calcium, magnesium, aluminum, zinc, iron and tin.
metal; hydrogen See formula on page 304
When an acid is added to a carbonate or bicarbonate (hydrogen carbonate), the products are __________ gas, ________ and an _______ ___________.
carbon dioxide gas, water and an ionic compound (salt). See page 305 for the formulas.
What is NEUTRALIZATION?
A reaction between an acid and a base to produce a salt and water.
The H+ of an acid (strong or weak) and the OH- of a strong base combine to form water as one product.
The salt is the cation from the base and the anion from the acid.
See page 305 for the equation and how to balance it.
What is TITRATION?
How do we accomplish this?
What is the NEUTRALIZATION ENDPOINT?
When we need to find the molarity of a solution of HCl, which has an unknown concentration, we do this by a laboratory procedure called TITRATION in which we neutralize an acid sample with a known amount of base.
We place a measured volume of the acid in a flask and add a few drops of an INDICATOR such as phenolphthalein (colorless in an acidic solution). Then we fill a buret with a NaOH solution of known molarity and carefully add NaOH solution to the acid in the flask.
In the titration, we neutralize the acid by adding a volume of base that contains a matching number of moles of OH-. When it changes to pink, neutralization has taken place. This is called the NEUTRALIZATION ENDPOINT.
From the volume added and molarity of the solution, we can calculate the number of moles of NaOH and then the concentration of the acid.
What is a BUFFER?
It is a solution that maintains pH by neutralizing added acid or base.
Ex: blood contains buffers that maintain a consistent pH of about 7.4
How does a BUFFER work?
In a buffer, an acid must be present to react with any OH- that is added, and a base must be available to react with any added H3O+.
However, the acid and base must not be able to neutralize each other. Therefore, a combination of an acid-base conjugate pair is used to prepare the buffer.
Most buffer solutions consist of nearly equal concentrations of a weak acid and a salt containing its conjugate base.
Buffers may also contain a weak base and a salt containing its conjugate acid.
See page 308 for the description of how this happens (formula)
