acids, bases & PH chp 20 Flashcards
what is a Bronsted-lowry acid
- acid dissociate and release H+ ions In aqueous solution
- Bronsted-lowry acid is a proton donor
what is a bronsted-lowry alkali
- dissociates into OH- ions in aqueous solution
- proton acceptor
what is a conjugate acid-base pair
- contains 2 species that can be interconverted by transfer of a proton
- In the forward direction, HCl (a conjugate base) releases a proton to form its conjugate, base, Cl-
- in the reverse direction, Cl- accepts a proton to form its conjugate acid, HCl
in this reaction how does each species act as either an acid or an alkaline
in the forward direction
- HCl is an acid as it donates H+
- OH- is a base and it accepts H+
in the reverse reaction
- H20 is an acid ac it donates H+
- Cl- is a base as it accepts H+
when could water act as a base
- can accpet protons from HCl to form H3O-
- What is meant by the terms monobasic, dibasic and tribasic
- give examples for each
- refers to the total numbers of hydrogen ions in the acid that can be replaced per molecule
- HCl = monobasic
- H2SO4 = dibasic
- H3PO4 = tribasic
what are some examples of mono basic, dibasic and tribasic acids
what is an ionic equation
A equation that shows the charges of the important elements involved
what are spectator ions
ions that do not change charge during the reaction, spectator ion is sulfategroup below
what type of reaction is the reaction between acids and metals
- redox reactions
what type of reaction is the reaction between neutralisation of acids with carbonates,metal oxides and alkalise
neutralisation
What does pH measure
hydrogen ion concentration
what do concentrations of hydrogen ion meant for pH
- A low value of [H+(aq)] matches a high value of pH
- A high value of [H+(aq)] matches a low value of pH
whats the formula for pH and [H+]
- pH=-log(10)[H+(aq)]
- [H+(aq)]= 10^-pH
how do the pH values differ
- pH of 1 has 10 time the concentration of H+ ions as a solution with a pH of 2
- to dilute a solution from a pH 1 to a pH of 4 qwould require dilution by 10x10x10=1000 times
how do the [H+] and [HA] relate when talking about strong acids
they are equal
what is Ka, what is its formula
- the acid dissociation constant
- it is Kc applies to the dissociation of an acid
what do the values of Ka tell us
- higher the Ka is further the equilibrium is to the right and the stronger the acid
^as acid dissociates more and gives larger value
what is the formula for pKa and the reverse formula
How do the strength of acids relate to the values of Ka and pKa
- the stronger the acid, the larger the Ka value and the smaller pKa value
- the weaker the acid the smaller the Ka value and the larger the pKa value
what’s the difference between a weak and strong acid
- a strong acid HA completely dissociates
- a weak acid HA partially dissociates
what does the [H+] depend upon for a weak acid
- concentration of acid
- acid dissociation constant, Ka
what are the assumptions made when calculating the Ka for a weak acid
- Assumption 1: The dissociation of water to form H+ ions is negligible when compared to H+ formed from acid
- Assumption 2:You can assume that HA > [H+], You can neglect any fall in concentration of HA from dissociation
How do you calculate pH using the Ka expression
Assumptions made when using calculations involving weak acids
- assumption 1: dissociation of water is negilible
- assumption 2: assumes the concentration of acid is much greater than the [H+] at equilibrium
how can water act both as a base and an acid
how can water act both as a base and an acid
- called ionic production of water
- can accepts hydrogen ions and acts as a base.
- can donate hydrogen ions and acts like as acid
From what can the pH of strong bases be calculated
- the concentration of the base
- the ionic product of water Kw
