Acids Flashcards
acids
key features
are sour
contain h+ ions
aqueous solution has a ph less than 7
Bases
key features
opposite of acids
aqueous solution has ph > 7.0
acids definition
equation
examples
acids dissociate in water
HX- H+ + X-
releases H+ ions into the solution
is a proton donor
HCL
HNO3
H2S04
CH3C00H
Alkali
definition
equation
examples
aqueous base
alkalis dissocate in water releasing OH- ions in the solution
X0H—- x+ OH-
common acids and their strengths
HCL- hydrochloric acid STRONG
HN03 - nitric acid STRONG
H2SO4 -sulphuric acid STRONG
CH3C00H - ethanoic acid WEAK
common bases and their strengths
Na0H - sodium hydroxide STRONG BASE (soluble)
KOH- potassium hydroxide STRONG BASE(soluble)
NH3 - ammonia WEAK BASE(soluble)
Ammonia as a base
Ammonia will dissolve in water forming a weakly alkaline solution
NH3+ + H2O (reversible equation sign) NH4+ OH-
weak base
definition of strength
measure of tendency to dissociate
strong acids and bases
fully dissociate in water
easily giving up protons or hydroxide ions
weak acids or bases
partially dissociate do not easily give up protons or hydroxide ions
definition of ph
measure of acidity or alkalinity
PH= -log(H+)
-log (H+)
Exam question- which of the below is a weak acid
A HCL
B H2SO4
C HNO3
D CH3COOH
answer= D ethanoic acid is a weak acid, it partially dissociates in water does not give up protons easily
Exam question= acids can be described as strong or weak. give a definition, example and equation to describe each.
a) strong
Strong acids fully dissociate in water releasing H+ ions in the solution
they give up protons easily, they are proton donors
example of a strong acid is HCL hydrochloric acid
equation =
XH—- X- + H+
(XH) acid
Exam Question= acids can be described as strong or weak. give a definition, example and equation to describe each
b) weak
Weak acids only partially dissociate in water releasing H+ ions in the solution. they do not give up protons easily
example= CH3C00H ethanoic acid
equation= XH ( reversible equation symbole) X- + H+
the reversible equation symbol represents partial dissociation.
are acids proton donors or acceptors
acids are proton donors, they donate H+ ions.
are acids proton donors or acceptors
acids are proton donors, they donate H+ ions.
are acids proton donors or acceptors
acids are proton donors, they donate H+ ions.
are bases proton acceptors or proton donors
bases are proton acceptors, they accept H+ ions
what are alkalis ( definition)
alkalis are aqueous bases that can dissolve in water
give examples of what bases can include
,metal oxides
metal hydroxides
metal carbonates
ammonia
they neutralise acids to form salts
Acids dissociate in water
equation
acids are proton donors that release H+ ions in aqueous solution
HX —– H+ + X-
name some common acids
hcl - hydrochloride STRONG
h2s04- sulphuric acid STRONG
hNO3 - nitric acid STRONG
CH3C00H - ethanoic acid WEAK
Alkalis also dissociate in water
give the equation
Alkalis are proton acceptors that release OH- ions in aqueous solution
XOH——– X+ + OH-
Name some common alkalis
KOH- potassium hydroxide STRONG
NaOH- sodium hydroxide STRONG
NH3- ammonia WEAK
we write H+ ions for simplicity however they are actually never found by themselves in an aqueous solution- they are always combined with H20 to form H3O+ hydroxonium ions
never found by themselves in aqueous solution
always combined with H2O to form H3O+ hydroxonium ions
strength of acid or base definition
measure of tendency to dissociate
strong acids will:
fully dissociate in aqueous solution as protons are lost easily ( donated)
e.g
HCL (aq) —– H+ + CL-
strong bases will
strong bases will fully dissociate in aqueous solution as hydroxide ions are easily lost
e.g
NaOH ( aq) —— Na+ + OH-
weak acids will:
weak acids will partially dissociate in aqueous solution and protons are not easily lost
e.g ethanoic acid
CH3C00H (reversible equation sign) CH3C00+ H+
weak bases will:
weak bases will partially dissociate as hydroxide ions are not easily lost
e.g ammonia
NH3 ( aq) + H2O ( aq) (reversible equation sign) NH4+ + 0H-
The reactions with strong acids and strong bases are also reversible however
the position of equilibrium is so far right that it can be replaced with a forward arrow as the amount the backwards reaction occurs at is negligible.
acid base titrations
titrations are a form of volumetric analysis where a known volume of solution and a known concentration is reacted with a measured volume of a different solution
this method can be used to find chemical unknowns such as:
-concentration
-molar mass
-water of crystalisation
- chemical formula
what is the end point
the solution in the conical flask becomes neutral at the end point
Titration method:
1) a measured volume of x is added to a conical flask using a pipette along with a suitable indicator such as phenolpthalein or methyl orange.
2) the burette is filled with the other solution y which has a known concentration.
3) the tap can be opened and a small quantity of y is released into conical flask. this is allowed to occur until the end point is reached, indicated by a colour change.
4) the volume of y that was added is measured and unknowns can then be calculated.
what are standard solutions
standard solutions are solutions of a known concentration. one of the solutions used in a titration must be a standard solution in order to calculate unknowns.
method to prepare a standard solution
1) carefully weigh out the required mass of solute
2) dissolve solute in chosen solvent in the beaker
3) transfer the solution to a volumetric flask. rinse the beaker with initial solvent and add washings to the flask
4) add more solvent into the volumetric flask until the level is nearly at the graduation line and not on the graduation line
5) add solvent drop by drop until the bottom of the meniscus sits on the graduation line
6) seal the volumetric flask and mix it thoroughly by inverting it multiple times ensuring that the stopper is on tightly
neutralisation occurs when?
an acid and a base react forming a salt and water
the general neutralisation reaction is
acid+ base—- salt + water
the ionic equation for a neutralisation reaction is
H+ + OH- —— H2O
salts are ionic compounds in which the H+ ion of an acid has been replaced with a metal ion or another positive ion
salts are ionic compounds in which the H+ ion of an acid has been replaced with a metal ion or another positive ion
salts are made up of a cation and an anion:
cation- positive ion, usually a metal ion or ammonium ion
anion- negative ion usually derived from an acid
example of a salt Na2SO4
cation:
anion:
cation - Na+
anion- so4 2-
acid + base=
salt plus water
metal + acid
salt + hydrogen gas
acid + metal oxide
salt + water
acid + metal carbonates
salt + water + carbon dioxide
acidic salts
are formed from
polyprotic acids( dissociate more than once, or donate more than one proton)
acidic salts can behave like acids
true or false
true- acidic salts can behave like acids
ammonium salts
give general equation for reaction
are formed when acids are neautralised by aqueous ammonia
HX+ NH3—— NH4X
example- ammonia reacts with nitric acid to produce ammonium nitrate
Nh3 (aq) + HNO3—- NH4NO3 (aq)
