Qualitative Analysis
Qualitative Analysis
1.
1. Qualitative Qualitative analysis analysis is is a a series oseries of f tests tests conducted conducted on on a a chemical chemical substance substance to to identifyidentify the salt component or components in it.
the salt component or components in it. 2.
2. Through Through qualitative qualitative analysis, analysis, thethe cationcation and and anionanion present in a salt are determined. present in a salt are determined. 3.
3. To To identify identify the the cation cation and and anion anion in in a a salt, thsalt, the folloe following wing tests are tests are usually usually conducted.conducted. Complete the diagram.
Complete the diagram.
1 1 UNKNOWN SALT UNKNOWN SALT 2. bserved colour 2. bserved colour of salts of salts 3. !dd distilled 3. !dd distilled water water 1. "hysical properties 1. "hysical properties NO NO22 SO SO442- 2-CO CO332- 2-Cl Cl22 CO CO22 NO NO33 --#. Te
#. Test for st for gasesgases $. %ffect of $. %ffect of heat heat Gas Gas released released Inference : Inference : Presence of Presence of Soluble?
Soluble? Reagent Reagent
&e &ess
'amp blue litmus 'amp blue litmus
paper paper (on in aqueous (on in aqueous solution solution ). Confirmatory ). Confirmatory
tests for ions tests for ions
*. Test for *. Test for cations cations +. Test for +. Test for specific cations specific cations . Test for . Test for anions anions *.a-sing sing /a0 /a0 * * b-sing sing /0 /033 aq-
aq-$. Colour of alts
a. ost salts are colourless aqueous solution or white salts.
b. alts of transition metals are coloured because they form coloured ions.
%4amples 5
Ion Colour
a- copper ((- ions, Cu26
b- iron ((- ions, 7e26
c- iron (((- ions, 7e36
c. Complete the following table 5
6 6 26 26 36 26 26 6
26
36
&ellow when hot white when cold
(nsoluble
9n
<rown when hot (nsoluble
#. Comfirmatory test for several gases.
a- Complete the following table 5
!as Colour S"ell
#$$e%t on da"& lit"us
'ea(en
t used Con$ir"atory test
0ydroge n Colourles s ;ighted splinter
Method 5 <ring a lighted splinter to the mouth of test tube.
Observation 5 :ives >??????> sound 4ygen dourles s :lowin g splinter Method 5 Observation 5 Carbon dio4ide dourles s ;ime
water Method 5 <ubble the gas producedinto ???????????????? Observation 5 !mmoni a Colourles s Chlorine :reenish yellow "ungent <lue to red, then ??????? /itrogen dio4ide "ungent ulphur dio4ide Colourles
s "ungent <lue to red
Method 5 Observation 5 0ydroge n chloride Colourles
s "ungent <lue to red
Method 5 'ip a glass rod in
concentrated ammonia solution an insert into the test tube
Observation 5 @hite fumes formed
heat
salt
Type og gas released
Colour of residue
Can predict the identity of
______
presence in salt
Can predict the identity of
________
presence in salt
). %ffect of 0eat on altsa- ost compounds which decompose leave behind o4ides.
alt
A
metal o4ide
6gas
residue identification gas identification refers to specific cation refers to
anion-
only-
b-c- 'raw the correct labeled diagram for the setBup to test carbon dio4ide gas liberated when the carbonate salt is heated strongly.
d- @rite down the chemical equations for the reactions that occur 5
Ion Carbonate salt Nitrate salt Sul&)ate salt C)loride salt
Is not decomposed by heat Decompose into O2 gas and metal
nitrite
Sulphate salts usually do not decompose
Chloride salts do not decompose except NH 4Cl
K * /o reaction 28/3A2 8/2 6 2 /o reaction /o reaction
Na* /o reaction /o reaction /o reaction
Decompose into metallic oxide and CO2
Decompose into metal oxide, NO2 and O2
Ca+* CaC
3 A Ca 6 C2 /o reaction /o reaction
M(+ *
/o reaction /o reaction
A,-* /o reaction /o reaction
ZnSO4 , CuSO4 and e2!SO4 "#
decompose $hen heated to produce metal oxide and SO#
.n+* /o reaction
e-* /o reaction
0b+* /o reaction /o reaction
Cu+* /o reaction
Decompose into metal, NO2 and O2
A(* /o reaction /o reaction
Decompose into NH # , CO2and $ater Decompose into nitrous oxide
N 2O and $ater
Sublimes $hen heated to produce NH # !g" and H 2 SO4 !g"
Sublimes $hen heated to produce NH # !g" and HCl !g"
N12 *
)
Carbonate 6 acid gas C2
Chloride 6 02$ gas 0Cl
,. Confirmatory test for anions
a- Complete the following diagram 5
*. Confirmatory test for cations
a- The presence of cation can be detected by using two common al=alis i- odium hydro4ide solution, /a0 and
ii- !mmonia solution, /03.
* Un3no4n Salt solution 6 ?????? 6 ?????? 6 02$ dilute 6 ??????? 6 ????????????? 6 dilute acid :as turns limewater ??????????? 6 0/3 6 ?????? ????????? precipitate formed ???????? ring formed ???????? ion confirmed ???????? ion confirmed ????????? ion confirmed $2B ion confirmed
The function of the al=alis is to produce a &re%i&itate, that is ?????????? ????????????????.
c- Complete the diagram below 5
d- Complete the diagram below 5
c- Con$ir"atory tests $or e+*5 e-*5 0b+* and N12*
11
d- Complete the following diagram to summarises the qualitative analysis of cations in salts.
e. (f a salt D is given as Einc nitrate, how can we test the compound to confirm the presence of 9n26 and /
3B ions in that saltF
Conduct the e4periment as follows 5
#&eri"ent Observation In$eren%e
1. bserved the colour of salt D • @hite salt
2. ??????? some solid D in a test tube and observe 5
a- the colour of gases released b- the effect on damp ????? litmus c- the effect on ????????? splint
d- observed the colour of residue when hot and cool. • ????????? gas. • ????? litmus turns ?????. • ????????? ????????? splint. • Gesidue colour 5 ?????? gas released. !cidic gas. 2 released. %robably NO#& present' %robably (((((( present' 3. !dd ????????? ????????? to D to ma=e solution. • ????????????
in water D is soluble salt
$. !dd ???????? ??????? solution, followed by ????????. i4. lowly, add #B) drops of ????????????? ???????? along test tube
side. 'o not
sha=e- ????????? ??????? formed.
Con)irms presence o) ????????, ????
#. To salt solution, ???????? a little /a0aq-, then add it to?????????.
*aybe ((((, ((((, or +l #.
). To salt solution, add a little ?????? aq-, then add it to ?????????.
???????? ?????????, soluble in e4cess /03.
Con)irms presence o) (((((( ion'
CONCLUSION 5 The ions present in salt D are confirmed as ????? and ????? ions.
Solid T
Solution Y + Gas V
Solid U + Gas V
Solution W
White precipitate soluble in excess
Solid U + Gas Y + Gas Z
+ dilute nitric acid Heated up
Heated up + dilute hydrochloric acid
+ aonia solution
Stru%tural question
1. 7igure 2 shows a flow chart summariEing the series of changes for a compound T.
olid is yellow in colour when hot and white in colour when cooled.
a- @hatissolidF H1mar=I
?????????????????????????????????????????????????????????????????????????????????
b- /ame the cation and anion in solid T. H 2 mar=s I
?????????????????????????????????????????????????????????????????????????????????
c - i- /ame gas J. H 1 mar= I
?????????????????????????????????????????????????????????????????????????????????
ii- @hat is observed when gas J is passed through limewaterF H 1 mar= I
?????????????????????????????????????????????????????????????????????????????????
iii- @rite the chemical equation for reaction between gas T with limewater. H 3 mar=sI ?????????????????????????????????????????????????????????????????????????????????
e- i- /ame solution &. H 1 mar= I
?????????????????????????????????????????????????????????????????????????????????
ii- 'escribe briefly a chemical test to identify the anion in solution &. H 3 mar=s I
?????????????????????????????????????????????????????????????????????????????????
?????????????????????????????????????????????????????????????????????????????????
?????????????????????????????????????????????????????????????????????????????????
f- /ame the type of reaction which occurs when solid reacts with dilute hydrochloric acid to form
solution@. H 1mar=I
?????????????????????????????????????????????????????????????????????????????????
g- i- @hat are gas & and gas 9 F H 2 mar=s I
?????????????????????????????????????????????????????????????????????????????????
ii- @rite the balance chemical equation for the effect of heat on solution &.H 1 mar= I
?????????????????????????????????????????????????????????????????????????????????
2. 7igure 3 summarises the series of reactions that involves lead compounds.
7igure 3
a- @hatissolidKF H1mar=I
b- @hat is the colour of solid K when hot and cooled F H 1 mar= I
c - @rite a balance chemical equation to represent the effect of heat on lead((- nitrate to form solid K and a
mi4ture of gas 8 and /. H 3 mar=s I
d- i- /ame precipitate . H 1 mar= I
ii- tate a way to test compound . H 1 mar= I
iii- @rite the ionic equation to show then formation of precipitate .
H 1 mar= I
e- odium hydro4ide solution is added little by little into solution / until there is no more change. @hat
can be observed F H 1 mar= I
f- 0ow can you obtain dry crystal salt, / , from solution / F H 3 mar=s I g- ! piece of Einc is put into solution /.
i- "redict the observation. H 1 mar= I
ii- @rite the chemical equation to represent the reaction which has occurred.
H 1 mar= I
1# 0eated up
i4 of gases 8 and ; 6 olid K ;ead((-nitrate !dd dilute nitric acid !dd dilute hydrochloric acid olution / @hite precipitate
Figure 3
-6 7igure 3 shows a series of process done by a student to identify a compound K.
a- @ith refer to reaction (, white precipitate Q is formed which is soluble in e4cess sodium hydro4ide solution. /ame all the ions which are probably presence in solution K.
H 1 mar= I
7 b- Geferring to reaction ( and ((, name the cation presence in solution K.H 1 mar= I
c - @rite down the ionic equation for the reaction forming the white precipitate, G.
H 3 mar=s I d- i- /ame two cations which produced white precipitate that will not dissolve
in e4cess sodium hydro4ide solution. H 1 mar= I
ii- tate one confirmatory test for one cation presence in d-i-. H 3 mar=s I
1) Gas K [Brown colour and acidified] + Gas L [Colourless] + Solid M Comound ! "ea# $issol%ed in wa#er &'i#e recii#a#e ( $issol%ed in e)cess sodium '*dro)ide solu#ion eac#ion ,, Colourless ! solu#ion &'i#e recii#a#e eac#ion ,