Chapter 20 Flashcards
What do acids release in water?
H⁺ ions
What do alkalis release in water?
OH⁻ ions
What is the Arrhenius model of acids and bases?
1) acids dissociate and release H⁺ ions in aqueous solution
2) alkalis dissociate and release OH⁻ ions in aqueous solution
3) H⁺ ions are neutralised by OH⁻ ions to form water:
H⁺(aq) + OH⁻(aq) –> H₂O)(l)
What is a Brønsted-Lowry acid?
proton donor
What is a Brønsted-Lowry base?
proton acceptor
What does the Brønsted-Lowry model for acids and bases emphasise?
The role of proton transfer between species
What is the equation showing the dissociation of hydrochloric acid, HCl(aq)?
HCl(aq) ⇌ H⁺(aq) + Cl⁻(aq)
Is HCl a strong or weak acid?
strong
What is a conjugate acid-base pair?
two species that can be interconverted by transfer of a proton
What is the formula for the hydronium ion?
H₃O⁺
What happens in dissociation?
A proton is transferred from an acid to a base
What is required to be present for dissociation to take place?
water
What is H₃O⁺(aq) often simplified to?
H⁺(aq)
What terms refer to the total number of hydrogen atoms in the acid that can be replaced per molecule in an acid-base reaction?
1) monobasic
2) dibasic
3) tribasic
What type of acid is HCl?
monobasic
What type of acid is CH₃COOH?
monobasic
What type of acid is H₂CO₃?
dibasic
What type of acid is H₃BO₃?
tribasic
HNO₃(aq) + NaOH(aq) –>
NaNO₃(aq) + H₂O(l)
H₂SO₄(aq) + 2NaOH(aq) –>
Na₂SO₄(aq) + 2H₂O(l)
H₃PO₄(aq) + 3NaOH(aq) –>
Na₃PO₄(aq) + 3H₂O(l)
What do acids react with to form salts?
1) metals
2) carbonates
3) metal oxides
4) alkalis
acid + metal –>
salt + hydrogen
2H⁺(aq) + Zn(s) –>
Zn²⁺(aq) +H₂(g)
Are carbonates acids or bases?
bases
acid + carbonate –>
salt + water + carbon dioxide
What is an acid neutralised by to form a salt and water only?
1) solid metal oxide
2) solid metal hydroxide
acid + base/alkali —>
salt + water
For any solution at 25°C:
1) pH less than 7 shows increasing acidity
2) pH greater than 7 shows increasing alkalinity
3) pH 7 is neutral
acid + base –>
acid + alkali –>
salt + water
2H⁺(aq) + MgO(s) –>
Mg²⁺(aq) + H₂O(l)
What is the ionic equation of neutralisation?
H⁺(aq) + OH⁻(aq) –> H₂O(l)
What is pH?
Simple numerical scale measuring hydrogen ion concentrations
For any solution at 25°C:
1) pH < 7 = increasing acidity
2) pH > 7 = increasing alkalinity
3) pH 7 = neutral
Does a low value of [H⁺(aq)] match a high or low pH?
high
Does a high value of [H⁺(aq)] match a high or low pH?
low
What is the mathematical relationship between pH and [H⁺(aq)]?
pH = -log[H⁺(aq)]
pH =
-log[H⁺(aq)]
What is the reverse of pH = -log[H⁺(aq)]?
[H⁺(aq)] = 10⁻ᵖᴴ
How many more H⁺ ions does a pH of 1 have than a pH of 2?
10 times
How many more H⁺ ions does a pH of 1 have than a pH of 14?
10¹³
[H⁺(aq)] =
10⁻ᵖᴴ
HA(aq) –>
H⁺(aq) + A⁻(aq)
For a strong acid, what is [H⁺(aq)] equal to?
the concentration of the acid, [HA(aq)]
For a strong acid, what can the pH be directly calculated from?
the concentration of the acid
What are the terms strong and weak used to describe?
The extent of dissociation of an acid
What is Kₐ?
the acid dissociation constant
What does the general formula HA(aq) –> H⁺(aq) + A⁻(aq) show?
The dissociation of any weak acid, HA
How is the acid dissociation constant Kₐ calculated?
Kₐ = [H⁺(aq)] [A⁻(aq)] / [HA(aq)]
What are the units of the acid dissociation constant, Kₐ?
mol dm⁻³
Is the Kₐ expression used for strong or weak acids?
weak
The larger the numerical value of Kₐ, the further the equilibrium is to which side?
right
pKₐ =
-logKₐ
What is the reverse of pKₐ = -logKₐ?
Kₐ = 10⁻ᵖᴷᵃ
The stronger the acid, the ___ the Kₐ value and the ___ the pKₐ value.
1) larger
2) smaller
The weaker the acid, the ___ the Kₐ value and the ___ the pKₐ value.
1) smaller
2) larger
When a strong acid HA completely dissociates, [H⁺(aq)] =
[HA(aq)]
When a weak acid partially dissociates, [H⁺(aq)] ≠
[HA(aq)]
What does [H⁺(aq)] depend upon?
1) the concentration of the acid, [HA(aq)]
2) the acid dissociation constant Kₐ
How can you determine the Kₐ for a weak acid experimentally?
1) preparing a standard solution of the weak acid of known concentration
2) measuring the pH of the standard solution using a pH meter
Is water an acid or a base?
both
H₂O(l) + H₂O(l) ⇌
H₃O⁺(aq) + OH⁻(aq)
What is Kᵥᵥ?
ionic product of water
Kᵥᵥ =
[H⁺(aq)] [OH⁻(aq)]
What is the value of Kᵥᵥ at 298K (25°C)?
1.00 x 10⁻¹⁴ mol² dm⁻⁶
What is the significance of Kᵥᵥ having a value of 1.00 x 10⁻¹⁴ mol² dm⁻⁶ at 25°C?
sets up the neutral point in the pH scale
What is an alkali?
A soluble base that releases OH⁻ ions in aqueous solution
What can the pH of a strong base be calculated from?
1) concentration of the base
2) ionic product of water Kᵥᵥ
