ACIDS & BASES Flashcards
What is the Bronsted-Lowry definition of acids and bases?
Acids- Proton donor
Bases- Proton acceptor
What is the trend in electronegativity across a periodic table?
Increases as you go across a period and as you go down a group.
What it a conjugate acid-base pair?
The species formed when an acid gives up a proton and can behave as a base.
When a base accepts a proton and can behave as an acid.
When is a conjugate base bad at accepting protons?
When the conjugate acid is better at losing protons.
When is a conjugate acid bad at losing protons?
When the conjugate base is better at accepting protons.
What is the definition of amphoteric?
A species that can acts as both acid and base
What is the rule regarding conjugates in acid-base reactions
Acids react with bases to give the conjugate base of the reactant acid.
The conjugate acid of the reactant base
Acid 1 + Base 2= Base 1 + Acid 2
What does an acid-base reaction in aqueous solution reveal?
Whether the reactant acid or the conjugate acid is strongest.
How can the concentration of hydrogen ions [H+] be deduced using the ionic product of water?
[H+]=Kw/[OH-]
What is the definition of a strong acid?
Dissociated completely in water to give H3O+ and the conjugate base (A-)
What is the definition of a weak acid?
Partially dissociates to give H3O+ and the conjugate base (A-)
What is Ka?
The acid dissociation constant
What does a larger Ka value indicate?
The greater degree to which the acid dissociates into its ions and the stronger acid
What happens to extent of acid dissociation in a more dilute solution? Why?
Increases. Equilibrium will shift to the right to oppose the change in the increase of water.
When should the [H+] due to the autoionisation of water not be ignored?
If the concentration of the solution is below 1x10-6
What is a polybasic acid?
Acids which are capable of losing more than 1 proton
What is a strong base?
one which fully dissociates into its ions in water
What is a buffer?
It is a solution which can resist changes in pH on addition of small quantities of acid or alkali or on dilution.
What is the ideal mixture of a buffer solution?
A mixture of a weak acid and its conjugate base.
What are the steps to calculating the pH of a strong base?
- Find out the conc of the solution
- Conc of strong base = [OH-]
- Use [H+]=[Kw]/[OH-]
What are the steps to calculating the pH of a weak acid?
- Identify the Ka of the acid
- Use Ka formula = [H+]^2/[HA]
- Rearrange formula
- [H}=/Ka{HA}
How to calculate the Ka of a weak acid?
- Identify the pH of the acid
- Inverse log the pH
- Use Ka formula (don’t forget to square [H+]!)
- Substitute the initial conc for [HA]
If given the pH how is the molarity calculated in a strong acid?
Change pH to a negative, then inverse log
Write an expression for pKa in terms of Ka
pKa= -log10Ka
