Acids and bases

Defintion of a bronsted lowry base

proton acceptor

Definition of a bronsted lowry acid

proton donor

How can H₂O act like an acid and a base

It can accept a proton to form a hydronium ion, and donate a proton to become a hydroxide ion

What type of acid is ethanoic acid (2 words)

weak monobasic

What type of acid is sulfuric acid

Strong dibasic acid

What does “p” mean in chemistry generally

-log of the quantity

Calculating pH for strong acids 

The acids fully dissociate, meaning [acid] = n[H⁺] where n is the number of hydrogens that the acid can donate

pH = ?

-log[H⁺]

General form for Ka (acid dissociation constant) and units

What is pK_a relationship to K_a

pK_a = -logK_a

How do K_a and pK_a vary depending on the strength of the acid

As acid strength increases, K_a increases and pK_a decreases

Expression for K_a of a weak acid (without approximations)

E

Expression for K_a for a weak acid with approximations 

Approximations for calculation pH of a weak acid

That the concentration of hydrogen ions are equal to the concentration of anions (there are some H+ from the water)

We assume the concentration of the acid at equilibrium is equal to the concentration of the acid at the start, as not a lot dissociates

K_w expression and value at 298K

10^-14 

How to calculate pH of a strong base

K_w/[OH-] = [H+] and n[OH-]→[base]

What is a buffer system

Reduces the effect of acids and bases on the system

What components make up a buffer solution

HA and A-

Ways to prepare buffer solutions

Using a salt and acid or partial neutralisation (excess of weak acid with a strong base)

What happens when H+ is added to a buffer solution

H+ ions react with conjugate base, the equilibrium shifts toward the acid which reduces the H+ ions

What happens when OH- is added to a buffer solution

OH- + H+ → H20, so equilibrium shifts toward the H+ + A- as HA dissociates

When [HA] = [A-]

pH = pKa

What is the healthy pH of blood, and the bounds in which pH is safe

7.4, 7.35-7.45

What is the buffer system in the blood

Carbonic acid

How to use a pH meter

You must calibrate the pH meter by dipping in a solution of known concentration of acid/alkali and a neutral solution, depending if we are using an excess of acid/alkali

What is the equivalence point of a titration

The centre of the vertical section of a pH curve, which is wherethe volume of one solution exactly reacts with the volume of the other solution

The colour of an end point to a titration

A colour inbetween the colour of the the conjugate base and weak acid

An indicator is a weak acid, which way is the equilibrium shifted toward when in excess of acid

To the left

At the end point, pKa =

pH

Over what range to indicators change colourq

2 pH

To choose a suitable indicator, what must the pH where it changes colour relate to in the titration

Should encompass the range where the vertical section of a titration is

Graph of strong acid - strong base titration

Graph of weak acid - strong base titration

Graph of strong acid - weak base titration

Graph of weak acid - weak base titration