Acid-Base And pH Flashcards by Bethany Emerson

What are the three definitions of acid-base?

Arrenhenius
Bronsted-Lowry
Lewis Theory

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What is the Arrhenius definition for acid and base?

Acid: produces hydrogen ion and an ion in water.
Base: produces hydroxide or hydroxyl ion and a cation in water.

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What is the Bronsted-Lowry definition of acid and base?

Acid: a proton donor
Base: a proton acceptor

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What is the Lewis theory definition of acid and base?

Acid: accepts electrons
Base: donates electrons

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What is a Brønsted-Lowry acid-base reaction?

A proton is transferred from an acid to a base.

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What is an amphirotic solvent?

A solvent that can act as an acid or base. (H2O)

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What are strong acids?

Powerful proton donors

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What are weak bases?

Conjugated base of strong acid.

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What is a strong base?

High tendency to accept protons.

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What is a weak acid?

Conjugate acid of a strong base.

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What value do strong acids have for Ka?

Large

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What value do weak acids have for Ka?

Small

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What does a smaller pKa mean?

Stronger acid
Weaker base
Large Ka

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What does a larger pKa mean?

Weaker acid
Strong base
Small Ka

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What is the value of pKw?

14
pKa+pKb

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How do we assess acidity?

Stabilisation of a conjugate base.
The more stable the conjugate base=more acidic is the compound

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How do we assess basicity?

Ability to use its nonbonding electrons to combine with a proton.

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What influences acidity and basicity?

Electronegativity
Bond energy
Inductive effects
Hybridisation effect
Resonance/ Delocalisation effects

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How does the increase of electronegativity influence acidity and basicity?

Increase acidity by stabilising negative charge of the conjugate base.
Decrease basicity as electrons of more electronegativity are less likely to be donated to a proton.

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How does bond energy influence acidity?

Increase as its able to disperse the negative charge over the atom weakening the bond strengths.

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How does inductive effect influence acidity?

Increase.

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How does the hybridisation effect influence acidity and basicity?

sp,sp2 and sp3 increase acidity
sp3,sp2 and sp increase basicity

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How does resonance/ delocalisation effects influence acidity?

Increase

How does a strong acid respond in water?

Completely ionise

How does a strong base react in water?

Completely dissociate

How do weak acids respond in water?

Not completely ionised

How do weak bases respond in water?

Not completely dissociate in water

What is the equation for Kw?

Kw=[H3O+][OH-]=10*-14

What is pKa a measurement for?

The point where the acid is half-neutralised

What is the outcome of increasing pH of an acid?

Acid becomes more ionised pH>pKa dissociated

What is the outcome of lowering the pH of an acid?

Acid becomes less ionised pH

What is the outcome of increasing pH of a base?

Base becomes less ionised pH>pKa undissociated

What is the outcome of lowering the pH of a base?

Base becomes more ionised pH

What is the equation for a neutralisation reaction?

Acid+ base—> Salt+ water

What happens to salt in a hydrolysis reaction?

Salt dissociate completely in water to reform the acid and base

What does a strong acid and strong base make?

Neutral Salt

What does a strong acid and weak base make?

Acidic salt

What does a weak acid and strong base make?

Basic salt

What is made when a neutral salt is put in water?

Neutral solution

What is made when acidic salt is put in water?

Acidic solution

What is made when basic salt is put in water?

Basic solution

What are acid-base titrations used for?

Quantitative analysis of the concentration of an unknown acid or base solution

What is the equivalence point in a titration mean?

Acid and base are in equal stoichiometric amounts

What is the half equivalence point in acid base titrations?

Half of the total amount of base needed to neutralise the acid that has been added

What is a buffer?

Solution containing two components which are weak acid and conjugate base or weak base and its conjugate acid

What does a buffer do?

Resist change in pH on addition of small amount of acid or base

What is buffer capacity?

The number of moles per litre of strong mono basic acid or base required to produce an increase of one pH unit in the solution

When is the maximum buffering power?

When pH=pKa

What are the different acids and bases?

Polyfunctional Oxoacids Acids and basic oxides

What are polyfunctional acids?

2 ionisable groups Difficult to dissociate more after loss of H+

What are oxoacids?

Contains an OH group that ionise in water and n-m doubly bonded

What are acidic and basic oxides?

Not obvious Hc donors or acceptors

When is an acid-base titration completed?

Hen all the acid has been converted into its conjugated base

What is the equivalence point of an acid-base titration?

Acid-base are in equal stoichiometric amounts

What can we use pKa values for?

Predict the outcome of acid-base interactions