Chemistry 152 Chapter 15
15. 74 Explain why small, highly charged metal ions are able to undergo hydrolysis?
such as Al³⁺, Cr³⁺, Fe³⁺, Bi³⁺, and Be²⁺. These can split H2O molecules, yielding acidic solutions.
15.14 Define pOH. Write the equation relating pH and pOH.
-the negative log of the hydroxide ion molarity pH= -log [H⁺] pOH= -log [OH⁻]
15.12 Define pH. Why do chemists normally choose to discuss the acidity of a solution in terms of pH rather than hydrogen ion concentrations, [H⁺]?
-the negative logarithm of the hydrogen ion concentration because it has no units or hard scientific notations
Ka is only associated with________?
weak acids
the stronger the acid the ______ the percent ionization.
greater
15.61 Carbonic acid is a diprotic acid. Explain what that means.
it means that for each unit of the acid yields two hydrogen ions upon ionization
15.3 Classify each of the following species as a Bronsted acid or base, or both: (a) H₂O, (b) OH⁻, (c) H₃O⁺, (d) NH₃, (e) NH₄⁺, (f) NH₂⁻, (g) NO₃⁻, (h) CO₃²⁻, (i) HBr, (j) HCN.
(a) both (b) both (c) acid (d) acid (e) acid (f) both (g) base (h) base (i) acid (j) acid
15.34 Classify each of the following species as a weak or strong base: (a) LiOH, (b) CN⁻, (c) H₂O (d) ClO₄⁻, (e) NH₂⁻
(a) strong (b) weak (c) neutral... (d) weak (e) weak
15.33 Classify each of the following species as a weak or strong acid: (a) HNO₃, (b) HF, (c) H₂SO₄, (d) HSO₄⁻, (e) H₂CO₃, (f) HCO₃⁻, (g) HCI, (h) HCN, (i) HNO₂
(a) strong (b) weak (c) strong (d) weak (e) weak (f) weak (g) strong (h) weak (i) weak
15.73 Define salt hydrolysis. Categorize salts according to how they affect the pH of a solution.
- the reaction of an anion or a cation of a salt, or both, with water. Salts that produce: Basic solutions Neutral solutions Acidic solutions
15.67 List four factors that affect the strength of an acid.
-The Polarity of the X--H Bond -The Size of the X Atom -The Charge on the Acid or Base -The Oxidation State of the Central Atom
15.39 What does the ionization constant tell us about the strength of an acid?
As the Ka value of an acid increases, so does the strength of the acid.
15.2 In order for a species to act as a Bronsted base, an atom in the species must possess a lone pair of electrons. Explain why this is so.
Because in order to have a Bronsted base it needs the addition of a proton to then conversely get its conjugateacid
15.30 H₂SO₄ is a strong acid, but HSO₄⁻ is a weak acid. Account for the difference in strength of these two related species.
Because it has less H⁺ ions
Why can we mostly ignore the H⁺ ions produced by the autoionization of water?
Because its Kw is very small (1.0 X 10⁻¹⁴) which means that water is not a significant contributor to the H⁺ ion concentration
15.41 Why do normally not quote Ka values for strong acids such as HCl and HNO₃? Why is it necessary to specify temperature when giving Ka values?
Because, essentially, the Ka is immeasurable, a really high value. The Ka relates the concentration of hydronium ion, acid anion, and original acid, such as acetic acid Ka = [H3O+][CH3COO-] / [CH3COOH] For a strong acid, the reaction essentially goes to completion, there is no equilibrium present. Thus, you cannot use an equilibrium constant to represent it. If you tried, the number would be really large, because the strong acid completely dissociates in water, all anions and hydronium, such as HCl HCl + H2O -> H3O+ + Cl- Strong acids are essentially completely ionized in solution, not in equilibrium, and cannot be accurately or usefully related with an equilibrium constant. because it is essential for the equation
15.29 What are the strongest acid and strongest base that can exist in water?
H₃O⁺ (acid) & OH- (base)
15.9 What is the ion-product constant for water?
Kw
When an acid is diluted, the concentration of the "particles" in the solution is reduced. According to __________ principle, this reduction in particle concentration (the stress) is counteracted by shifting the reaction to the side with more particles (meaning the equilibrium shifts from the nonionized acid side (one particle) to the side containing H⁺ ions and the conjugate base (two particles) HA⇌H° + A⁻.
Le Chatelier's
15.91 What are the Lewis definitions of an acid and a base? In what way are they more general than the Bronsted definitions?
Lewis base- a substance that can donate a pair of electrons Lewis acid- a substance that can accept a pair of electrons
15.28 Without referring to the text, write the formulas of four strong acids and four weak acids.
SA- HCL, HNO₃, HClO₄, H₂SO₄ WA- HF, CH₃COOH, NH₄⁺
15.27 Explain what is meant by the strength of an acid.
The acidity as in how acidic is the acid (strong or weak)
15.1 Define Bronsted acids and bases. Give an example of a conjugate pair in an acid-base reaction.
The conjugate base of a Bronsted acid is the species that remains when one proton has been removed from the acid A conjugate acid results from the addition of a proton to a Bronsted base
15.68 How does the strength of an oxoacid depend on the electronegativety and oxidation number of the central atom?
The electronegativity of the central atom and the number of O atoms determine oxoacid acidity. With the same central atom, acid strength increases as the number of oxygen attached to the central atom increases. With the same number of oxygens around the central atom, acid strength increases with the electronegativity of the central atom.
15.10 Write an equation relating [H⁺] and [OH-] in solution at 25°C.
[H⁺][OH⁻]= 10⁻¹⁴ (Kw)
what is Ka?
acid ionization constant
a high degree of ______ characterizes a ______ acid
polarity, stronger
What does the strength of an acid depend on?
properties of the solvent temperature molecular structure of the acid
15.40 List the factors on which the Ka of a weak acid depends.
strength electronegativity
