pH of Acids and Bases - Equilibria Pt B - (5.1) Flashcards
What does Arrhenius’ theory state?
- acids = substances that dissociate in water to give H+ ions
- bases = substances that dissociate in water to give OH- ions
- neutralisation happens when the 2 ions combine to give water
What happens in the Brønsted- Lowry Theory?
Acid = substances that donate protons Bases = substances that can accept protons
What does the Lewis theory state?
Acids = substances that can accept a pair of electrons Bases = substances that can donate a pair of electrons
What are strong acids and bases?
- fully dissociate in water
- equilibrium lies to the right to remove the sign + replace it with an arrow
Give some examples of strong acids.
HCl and H2SO4
Give some examples of strong bases.
NaOH, LiOH and KOH
What are weak acids and bases?
- they partially dissociate in solution
- its equilibrium can lie in any position (depending on the acid/base)
Most acids in biological processes are weak acids. True or False?
True - e.g. ethanoic acid (vinegar) or ammonia
What is the pH scale?
- measure of the concentration of H3O+ ions in solution
- on a scale of 1 - 14
(extreme conditions exist where the pH is not between 0 - 14)
Equation for calculating pH:
pH = -log10 [H3O+]
Equation to calculate H+ ions:
[H3O+] = 10 ^-pH
What is the Ka?
Acid Dissociation constant
Why is water not included in the equation for Ka?
- because its constant is almost constant for dilute solutions so it can be incorporated
What are the steps for finding the pH of an acid with Ka?
- Write an equation
- Write an expression for Ka
- Simplify the expression for Ka
- Make assumptions
- Rearrange the equation
- Solve the equation
- Calculate pH
