8 salts
DESCRIPTION
saltTRANSCRIPT
SALTS
Synthesising salts
Synthesising qualitative analysis
of salts
Practising to be systematic and
meticulous when carrying activities
1. Define salts2. Give 3 examples of soluble salt. 3. Give 3 examples of insoluble salt 4. Describe an experiment to prepare a soluble salt.5. Describe an experiment to prepare an insoluble salt
1. State the meaning of qualitative analysis.2. Describe the tests for Pb2+, Zn2+ and Mg2+.3. Describe confirmatory tests for Fe2+, Fe3+, Pb2+ and NH4+.4. Describe the test for SO42-5. Plan qualitative analysis to identify a sample of salt.6. Describe the test for oxygen gas.
Chapter 8 T. 8.0
8.1
8.28.3
SALTS
Definition
Examples
Solubility of salts
Preparation of salt
Crystal1. Definition
2. Properties
Salts are an ionic compound whereH+ from an acid has been replace by metal ion or ammonium ion.
NaClCuI2
BaSO4
Pb(NO3)2
(NH4)2CO3
Preparation of the soluble salts
Preparation of insoluble salts
Experiment
Examples
Examples calculations involving salts Ionic equation
Experiment to build ion equation by continuous change method
*T.8.1.1
Salt Solubility in water
NitrateSulphateChlorideCarbonate
All solubleall except BaSO4 , PbSO4 , CaSO4
all except Hg2Cl2, AgCl, PbCl2
non soluble except K2CO3, Na2CO3, (NH4)2CO3
Method:1.Acid and alkali reaction2.Acid and base reaction3.Acid and metal reaction4.Acid and carbonate reaction.
T. 8.1
Method: Double decomposition
Soluble salt + soluble salt soluble salt + insoluble salt
Sodium chloride
8.0 SALTS
A. What is salt?Students should be able to explain the meaning of salt.
Do you know what is salt?
1. Complete the following diagram :
Formula :
Consist
cation anion
Do you still remember that salt is formed in neutralization?
AcidBase/alkali
Comes fromComes from
Example
NaOH + HCl NaCl + H2O
Definition :Salts are _______ __________ formed when _________ ____, H+ from acid is replaced with _______ ______ or an ___________ _____, NH4
+
from base or alkali
Metal ion Non-metal
2. The following diagrams show the formation of salt from an acid. Fill in the box with the appropriate acid and salt produce.
a) Formation of salt from hydrochloric acid chloride salt
b) Formation of salt from _____________ nitrate salt
c) Formation of salt from sulphuric acid ____________ salt
d) Formation of salt from carbonic acid ______________ salt
NH4+
Na+
ClNH4
ClNa
ClH
NH4+
K+
H
NH4+
Mg2+
NH4+
Na+
B. Soluble and insoluble salt Students should be able to identify soluble and insoluble salts.
** All metal oxides and hydroxides are insoluble in water except Na2O, K2O, NaOH, KOH and NH4OH. Ba(OH)2 and Ca(OH)2 are slightly soluble in water.
2. Write down the chemical formula of salts:
Metal ionSulphate salt(from H2SO4)
Chloride salt(from HCl)
Nitrate salt(from HNO3)
Carbonate salt(from H2CO3)
K+
Na+
Ca2+
Mg2+
Al3+
Zn2+
Fe2+
Pb2+
Cu2+
Ag+
Ba2+
NH4+
Table 8.1
PCB
EXCEPT
EXCEPT• All sulphate salts are soluble PbSO4, CaSO4 and BaSO4.
• All chloride salts are soluble PbCl2, AgCl and HgCl2
• All K+, Na+ and NH4+ salts are soluble.
• All nitrate salts are soluble.
insolublesoluble
SALT
• All carbonate salts are insoluble K2CO3, Na2CO3 and (NH4)2CO3
(soluble)
PAH
ANaK
3. From the above table (Table 8.1) name six examples of soluble salts and six examples of insoluble salts.
SOLUBLE SALT INSOLUBLE SALT
1. 1.
2. 2.
3. 3.
4. 4.
5. 5.
6. 6.
Table 8.2
C. Preparing SaltsStudents should be able to describe the preparation of soluble salts and insoluble salts.
1. Complete the diagram on next page…
heatheat
heat
PREPARING SALT
SOLUBLE SALT INSOLUBLE SALT
NH4+, Na+, K+ Other than
NH4+, Na+, K+
Acid + alkali ______ + ______
titration
Method I
Acid + metal oxide ______ + ______
Acid + metal ______ + __________
Acid + metal carbonate ______ + ______ + _______
Neutralisation
Method II
Acid is titrated to alkali until neutral by using an indicator. Repeat without the indicator to get _______ salt.
Add metal/ base oxide/ metal carbonate until ___________
Undissolved metal/ base oxide/ metal carbonate
_____________ the filtrate until saturated solution is formed.
Cool it at room temperature until __________ are formed.
Salt crystal
Filter the mixture to separate _____ _________
_______ the salt crystal with _________ _______
Salt solution
Double decomposition method/ Precipitation reaction
Method III
Pb(NO3)2 (aq) + 2NaCl (aq) PbCl2 (s) + 2NaNO3 (aq)
2. Preparing insoluble salts by precipitation reaction
Aqueous solution + aqueous solution precipitate + aqueous solutionorsoluble salt solution + soluble salt solution insoluble salt + soluble salt solution
examples : Preparing lead (II) chloride salt
Pb(NO3)2 (aq) + 2NaCl (aq) PbCl2 (s) + 2NaNO3 (aq)
Aqueous solution Aqueous solution
containing Pb2+ containing Cl-
Mix two ___________ __________
Stir with a ________ ________
Filter & wash with _______ ______
_____ the salts with filter paper
White precipitate of lead (II) chloride
Cl-
Na+
NO3-
NO3-
Pb2+
+
Cl-Cl-Pb2+ NO3
- Na+
precipitate
Choose any solution containing Pb2+ ion
Choose any solution containing Cl- ion
precipitate(Insoluble salt)
3. Complete the following table and write all the possible chemical equation and ionic equation to prepare salts :
SaltType of
saltChemical equation Ionic equation
Magnesium sulphate
Soluble
MgO (s)+ H2SO4 (aq) MgSO4 (aq)+ H2O (l)MgO + 2H+ + SO4
2- Mg2+ + SO42- + H2O
MgO + 2H+ Mg2+ + H2OMg (s) + H2SO4 (aq) MgSO4 (aq) + H2 (g)
MgCO3 (s) + H2SO4 (aq) MgSO4 (aq) + H2O (l)+ CO2 (g)
Pottasium nitrate
Soluble H+ + OH- H2O
Lead (II) chloride
Insoluble
Pb(NO3)2 (aq) + 2NaCl (aq) PbCl2 (s) + 2NaNO3 (aq)
Pb2+ + Cl- PbCl2
Pb(NO3)2 (aq) + 2HCl (aq) PbCl2 (s) + 2HNO3 (aq)
Copper (II) sulphate
Lead (II) nitrate
Ammonium sulphate
SaltType of
saltChemical equation Ionic equation
Aluminium carbonate
Silver chloride
Iron (II) nitrate
Zinc chloride
Barium sulphate
Sodium carbonate
Table 8.3
4. Physical characteristics of crystals
D. Constructing ionic equation using the continuous variation method.
The ionic equation for the formation of an insoluble salt can be constructed if we know the number of _______ of cation and anion reacted together to form ______ of insoluble salt. (…Refer next page)
Examples :
1 mole of silver chromate (VI) is formed from 2 moles of Ag+ ions and 1 mole of CrO42- ions.
Ionic Equation : 2Ag+ (aq) + CrO42- (aq) Ag2CrO4 (s)
TRY THIS :
1 mole of lead (II) iodide is formed from 1 moles of Pb2+ ions and 2 mole of I- ions.
Ionic Equation :
_______ geometrical shapes
Crystals of the same substance have same
_______ but may be in different _______.
Fixed ______ between two neighbouring
surfaces
Crystals have _______ surfaces, straight
edges and ________ angles.
Height of Precipitate (cm)
5
0 5 Vol. of BaCl2 (cm3)
IONIC EQUATION(Using continuous variation method)
Experiment: Precipitation of barium chromate (VI)
The ratio of the number of moles of cation and anion reacted together to form 1 mole of insoluble salt.
From graph:5 cm3 of K2CrO4 reacted equivalent to 5 cm3 BaCl2
No. of mole CrO42- = MV/1000 = 0.5 x 5/1000 = 0.0025 mole
No. of mole Ba2+ = MV/1000 = 0.5 x 5/1000 = 0.0025 mole
No. of mole Ba2+: No. of mole CrO42-
0.0025 moles : 0.0025 molesOr 1 : 1
Therefore ionic equation is, Ba2+ + CrO42- BaCrO4
Chemical equation, K2CrO4 + BaCl2 BaCrO4 + 2KCl
*T. 8.1.1
Test tube
potassium chromate 0.5 M (V cm3)
barium chloride 0.5 M (V cm3)
Height of precipitate (cm) 1.1 2.2 3.3 4.4 5.5 5.5 5.5
Writing the ionic equation : 1.
2.
TRY THIS :
10 cm3 of 0.25 mol dm-3 lead(II) nitrate solutions react completely with 10cm3 of 0.5 mol dm-3 pottasium chloride solution. A white precipitate of lead (II) chloride is formed. Construct the ionic equation for the formation of lead (II) chloride.
Solution :
Number of moles of Pb2+ ions in lead (II) nitrate solution : n = MV 1000
=
= ___________ mol
Number of moles of Cl- ions in potassium chloride solution : n = MV 1000
=
= ___________ mol
From the calculation the ratio of Pb2+ ions : Cl- ions = _________ : _________
So, the simplest ratio of Pb2+ ions : Cl- ions = ________ : ________
Ionic equation :
E. Numerical problems involving stoichiometric reactions in the preparation of salts
Complete the relationship in the following diagram :
Do you still remember…..The relationship between the number of
moles, mass, the number of particles, volume of gas and concentration of
reactants and products?
Mass
Number of particles
Volume of gas
Concentration
Number of moles
HOW TO SOLVE THE NUMERICAL PROBLEM ????
Calculation steps :
S1 : Write the balanced equationsS2 : Write the information from the question below the equationS3 : Write the information from the equation below the chemical involvedS4 : Change S2 information into mol using the mole conceptS5 : Compare the mole ratio between the reactants and the products involved in the reaction.S6 : Change the information into the required unit using the appropriate formula.
Example :
A student prepares copper (II) nitrate by reacting copper (II) oxide powder with 100cm3 of 1.5 mol dm-3 nitric acid. Calculate the mass of copper (II) oxide needed to react completely with the acid. [Relative atomic mass : Cu, 64; O, 16]
S1 : CuO + 2HNO3 Cu(NO3)2 + H2OS3 : 1 mol 2 mol S2 : V=100cm3
M=1.5 mol dm-3
S4 : the number of moles of HNO3 ==> n = M V 1000 = 1.5 x 100 1000 = 0.15 mol
S5 : From the chemical equation, 2 mol of HNO3 reacted with 1 mol of CuO Therefore, 0.15 mol of HNO3 reacted with 0.075 mol of CuO
S6 : The mass of CuO = 0.075 mol x (64 + 16) gmol-
= 6.0 g
TRY THIS :
1. Acid reacts with calcium carbonate in limestone to form a salt and carbon dioxide. A piece of limestone reacted completely with 50cm3 0.1moldm-3 hydrochloric acid. [Relative atomic mass : H, 1; C, 12; Cl, 35.5; O, 16; Ca, 40;Molar volume: 24dm3 mol-1 at room temperature]
a) Calculate the mass of salt produced.
b) What is the volume of carbon dioxide liberated at room conditions?
QUALITATIVE ANALYSIS OF SALTS
Early observation
Colour of salts Solubility
Effect of heat on salts
The ion test
Cation test
Anion test
Using NaOH and NH4OH in excess
Confirmation test
*T.8.2.1
Anion introduction test:Anion confirmation test:
ReferT.8.1
To know the unknown salt
Experiment
Green Fe2+, CuCO3 Brown Fe3+Blue Cu2+White most of salts
Gas test
Carbonate Carbonate salts metal oxide + CO2Nitrate (i) Nitrate salts metal oxide + NO2 + O2 (ii) Potassium & sodium nitrate metal Nitrite + O2 (iii) Ammonium nitrate N2O + H2OSulphate (i) Sulphate salts metal oxide + SO3 and/ SO2 (ii)Sulphate salts of Group 1 and 2 are not decomposeChloride Not decompose except the ammonium chloride
T. 8.2
Qualitative Analysis
1. Qualitative analysis is a series of tests conducted on a chemical substance to identify
the salt component or components in it.
2. Through qualitative analysis, the cation and anion present in a salt are determined.
3. To identify the cation and anion in a salt, the following tests are usually conducted. Complete the diagram.
UNKNOWN SALT
1. Physical properties
2. Observed colour of salts
4. Effect of heat
5. Test for gases
Soluble
3. Add distilled water
Ion in aqueous solution
6. Confirmatory tests for ions
7. Test for anions
8. Test for cations
Yes
9. Test for specific cations
CO2
Cl2
NO2
CO32-
SO42-
NO3 -
Reagent
Damp blue litmus paper
Inference : Presence of
Gas released
8.a)Using NaOH
8 b)Using
NH3 (aq)
4. Colour of Salts
a. Most salts are colourless aqueous solution or white salts.
b. Salts of transition metals are coloured because they form coloured ions. Examples :
Ion Colour
(a) copper (II) ions, Cu2+
(b) iron (II) ions, Fe2+
(c) iron (III) ions, Fe3+
c. Complete the following table :
Solid Aqueous Salts/Metal oxide
Colourless K+, Na+, Ca2+, Mg2+, Al3+, Zn2+, Pb2+, NH+
Green Insoluble
Light green Fe2+ example: FeSO4 ,FeCl2 ,Fe(NO3)2
Blue Blue
Brown Fe3+
Black CuO
Yellow when hot white when cold
Insoluble
ZnO
Brown when hot yellow when cold
Insoluble
a) Complete the following table :
Gas Colour SmellEffect on
damp litmus paper
Reagent used
Confirmatory test
Hydrogen
Colourless
Lighted splinter
Method : Bring a lighted splinter to the mouth of test tube.Observation : Gives '______' sound
OxygenOdourless
Glowing splinter
Method :
Observation :
Carbon dioxide
Odourless
Lime water
Method : Bubble the gas produced into ________________ Observation :
Ammonia
Colourless
ChlorineGreenish yellow
PungentBlue to red, then _______
Nitrogen dioxide
Pungent
Sulphur dioxide
Colourless
Pungent Blue to red
Method :
Observation :
Hydrogen chloride
Colourless
Pungent Blue to redMethod : Dip a glass rod in concentrated ammonia solution an insert into the test tubeObservation : White fumes formed
6. Effect of Heat on Salts
a) Most compounds which decompose leave behind oxides.
Salt → metal oxide + gas (residue identification (gas identification
refers to specific cation refers to anion) only)
b)
c) Draw the correct labeled diagram for the set-up to test carbon dioxide gas liberated when the carbonate salt is heated strongly.
Can predict the identity of ________
presence in salt
Can predict the identity of
______ presence in salt
Colour of residueType og gas released
salt
heat
d) Write down the chemical equations for the reactions that occur :
Ion Carbonate salt Nitrate salt Sulphate salt Chloride 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 NH4Cl
K+ No reaction 2KNO3 →2 KNO2 + O2 No reaction No reaction
Na+ No reaction No reaction No reaction
Decompose into metallic oxide and CO2
Decompose into metal oxide, NO2 and O2
Ca2+ CaCO3 → CaO + CO2 No reaction No reaction
Mg2+
No reaction No reaction
A13+ No reaction No reactionZnSO4, CuSO4 and Fe2(SO4)3
decompose when heated to produce metal oxide and SO3
Zn2+ No reaction
Fe3+ No reaction
Pb2+ No reaction No reaction
Cu2+ No reaction
Decompose into metal, NO2 and O2
Ag+ No reaction No reactionDecompose into NH3, CO2 and water Decompose into nitrous oxide
N2O and waterSublimes when heated to produce NH3 (g) and H2SO4 (g)
Sublimes when heated to produce NH3 (g) and HCl (g)
NH4
+
a) Complete the following diagram :
8. Confirmatory test for cations
a) The presence of cation can be detected by using two common alkalis
i) Sodium hydroxide solution, NaOH and
ii) Ammonia solution, NH3.
Unknown Salt solution
Gas turns limewater
___________
_________ precipitate
formed
________ ring formed
________ ion confirmed
SO42- ion
confirmed________ ion
confirmed_________ ion
confirmed
+ dilute acid
+ HNO3
+ ______+ ______+ ______
+ H2SO4 dilute+ _______+ _____________
The function of the alkalis is to produce a precipitate, that is __________ ________________.
Metal ion + hydroxide ion metal hydroxide
e. If a salt X is given as zinc nitrate, how can we test the compound to confirm the presence of Zn2+ and NO3
- ions in that salt?
Conduct the experiment as follows :
Experiment Observation Inference1. Observed the colour of salt X White salt
2. _______ some solid X in a test tube and observe : (a) the colour of gases released (b) the effect on damp _____ litmus (c) the effect on _________ splintd) observed the colour of residue when hot
and cool.
_________ gas.
_____ litmus turns _____.
_________ _________ splint.
Residue colour :Hot : _________Cool : _________
______ gas released. Acidic gas.
O2 released.
Probably NO3- present.
Probably ______ present.
3. Add _________ _________ to X to make solution.
____________ in water X is soluble salt
4. Add ________ _______ solution, followed by ________. Mix. Slowly, add 5-6 drops of _____________ ________ along test tube side. (Do not shake)
_________ _______ formed.
Confirms presence of ________, ____
5. To salt solution, ________ a little NaOH(aq), then add it to_________.
Maybe ____, ____, or Al3+.
6. To salt solution, add a little ______ (aq), then add it to _________.
________ _________, soluble in excess NH3.
Confirms presence of ______ ion.
CONCLUSION : The ions present in salt X are confirmed as _____ and _____ ions.
EXECISES
1. Among the following cation solutions, which will produce precipitate when mixed with excess ammonia solution ?
I Aqueous solution Zn 2+
II Aqueous solution Pb 2+
III Aqueous solution Mg 2+
IV Aqueous solution Al 3+
A I onlyB I and IV onlyC I,II and IV onlyD II, III, and IV only
2. Among the following compounds, which is solube in water?
A lead(II) chlorideB zinc carbonateC lead(II) nitrateD Barium sulphate
3. Among the following ions, which will produce precipitation when added with hydrochloric acid solution ?
I Ca 2+ ionII Pb 2+ ionIII Ag + ionIV Al 3+ ion
A I and II onlyB II and III onlyC I, II and III onlyD I, II, III and IV
4. Figure 3 shows a flow chart for a series of reactions.
Among the following, which may be compound X ?
A copper(II) oxideB iron(III) nitrateC copper(II) carbonateD lead(II) nitrate
5. The reaction between silver nitrate solution and potassium carbonate produces an insoluble salt X. Among
XBlack solid
Blue solution
Heated up
Hot hydrochloric acid is added
the following solutions, which can dissolve salt X ?
A ammonia solutionB sodium hydroxide solutionC dilute sulphuric acidD barium chloride solution
6. Figure 5 shows tests performed on compound G.
Figure 5
G is a mixture of two types of salts. Among the following, which is found in G ?
A silver sulphate and copper(II) carbonateB lead(II) nitrate and zinc carbonateC lead(II) nitrate and aluminium nitrateD magnesium sulphate and lead(II) carbonate
7. Which of the following ions form a white precipitate that dissolves in excess sodium hydroxide solution ?
I Al 3+
II Mg 2+
III Pb 2+
IV Zn 2+
A I and III onlyB II and IV onlyC I,II and III onlyD I,III and IV only
8. A precipitate is formed when solution X is added to solution Y. Among the following, which represents solution X and Y ?
G
Precipitation solution
Added with dilute hydrochloric acid and filtered
White precipitatedissolve
Added with ammonia solution until in excess
Solution X solution Y
A sulphuric acid sodium carbonateB silver nitrate hydrochloric acidC zinc nitrate potassium iodideD aluminium sulphate sodium chloride
9. Table 2 shows the results of tests performed on a compound Y.
Test ObservationHydrochloric acid is added. Product formed is heated up slowly
White precipitate formed dissolves when heated up
Barium hydroxide solution is added
White precipitate formed
What is compound Y ?
A zinc sulphateB lead(II) chlorideC silver nitrateD lead(II) sulphate
Test Observation
Sodium hydroxide solution is slowly added until excess.
White precipitate formed.The white precipitate dissolves in excess
sodium hydroxide solution.
A few drops of sulphuric acid is added White precipitate formed.
10. The table above shows the observations made for a test conducted on a colorless solution. Among the ions below, which ion will probably exist in the solution?
A Al 3+ B Mg 2+ C Pb 2+ D Zn 2+
11. 10 g of magnesium carbonate powder, MgCO3 is reacted with 100 cm3 of sulphuric acid, H2SO4 1 mol dm-3. What is the mass of magnesium carbonate that is not reacted?
[Relative atomic mass: Mg, 24; C, 12; O, 16] A 0.84 g B 1.60 g C 8.40 g D 9.16 g
12. Which of the following method is suitable for preparing silver chloride in the laboratory?
A Heating silver metal with chlorine gasB Adding silver powder to dilute hydrochloric acidC Adding silver oxide to dilute hydrochloric acidD Adding silver nitrate solution to dilute hydrochloric acid
13. Which of the following equations represents the reaction that can produce lead(II) iodide crystal?
A PbO + 2KI → PbI2 + K2OB PbSO4 + 2KI → PbI2 + K2SO4
C Pb(NO3)2 + 2KI → PbI2 + 2KNO3
D PbCl2 + 2KI → PbI2 + 2KCl
14. When solid R is heated strongly, the residue produced is yellow in colour when cold. What is solid R? A Lead(II) carbonate B Calcium carbonate C Sodium carbonate D Zinc carbonate
15. The table below shows the results of the tests carried out on an unknown colourless solution.
Test ObservationSodium hydroxide solution is added gradually to the solution until in excess.
A white precipitate is formed.The precipitate is soluble in excess sodium hydroxide solution.
Aqueous ammonia is added gradually to the solution until in excess.
A white precipitate is formed.The precipitate is insoluble in excess aqueous ammonia.
Sulphuric acid is added to the solution. No changes.
Which of the following ions may be present in that solution? A Al3+
B Mg2+
C Pb2+
D Zn2+
15. Lead(II) nitrate can be prepared by adding A lead(II) sulphate to dilute nitric acid.B lead(II) oxide to dilute nitric acid.C lead(II) chloride to potassium nitrate solution.D lead(II) carbonate to sodium nitrate solution.
16. The reaction between sulphur dioxide and potassium manganate(VII) solution can be represented by the following equation:
2KMnO4 + 5SO2 + 2H2O → K2SO4 + 2MnSO4 + 2H2SO4
What is the mass of sulfur dioxide that reacts completely with 1.0 dm3 potassium manganate(VII) solution 0.02 mol dm-3?[Relative atomic mass: O, 16; S, 12]
A g
B g C g
D g
1994
16. Solution Y contains two anions. A series of test is carried out on solution Y and the results are shown below.
Add dilute Add barium nitric acid chloride solution
Add silver nitrate solution
The ions present in solution Y are A sulphate ion and carbonate ion B nitrate ion and carbonate ion C sulphate ion and chloride ion D nitrate ion and chloride ion
17. According to the equation below, what is the volume of copper(II) sulphate solution 1 mol dm-3 required to react with 0.92 g metal Q? [Relative atomic mass: Q, 23]
2Q + CuSO4 → Q2SO4 + CuA 15 cm3
B 20 cm3
C 30 cm3
D 60 cm3
18. When aqueous ammonia is added to copper(II) sulphate solution, a blue precipitate is formed. What happens to
the blue precipitate when aqueous ammonia is added until in excess?A Cannot dissolve in excess aqueous ammoniaB Dissolves in excess aqueous ammonia to produce a dark blue solutionC Dissolves in excess aqueous ammonia to produce a colourless solutionD Cannot dissolve in excess aqueous ammonia but changes to a dark blue
precipitate
19. Which of the following schemes is used to identify sulphate ion in soluble salt?
A dissolve in dilute Add barium
hydrochloric acid chloride solution
B dissolve in dilute Add barium
Solution Y Colourlesssolution
Whiteprecipitate
Whiteprecipitate
Sulphate salt
Whiteprecipitate
Solutionformed
Sulphate salt
Whiteprecipitate
Solution formed
sulphuric acid chloride solution
C dissolve Add dilute Add barium In water sulphuric chloride acid solution
D dissolve Add dilute Add barium In water hydrochloric chloride acid solution
20. Which of the following solid salts can be prepared by double decomposition reaction?A Lead(II) nitrateB Silver chlorideC Magnesium sulphateD Sodium carbonate
21 A dilute acid Q is added to a base R until in excess and then shaken. A white precipitate is formed. Which of the following pairs of Q and R represents the reaction?
Q R A Hydrochloric acid Lead(II) oxideB Sulphuric acid Zinc oxideC Sulphuric acid Copper(II) oxideD Nitric acid Magnesium oxide
22. The reaction between barium chloride and silver nitrate can be represented by the equation below.
BaCl2(aq) + 2AgNO3(aq) → 2AgCl(s) + Ba(NO3)2(aq) Which of the following barium chloride solution can exactly react with 20.0 cm3 silver nitrate solution 0.5 mol dm-3?
A 20.0 cm3 barium chloride solution 1.0 mol dm-3
B 10.0 cm3 barium chloride solution 0.5 mol dm-3
C 20.0 cm3 barium chloride solution 0.5 mol dm-3
D 40.0 cm3 barium chloride solution 0.5 mol dm-3
23. When substance T is heated in air, a brown gas which can turn moist blue litmus paper red is produced. The residue formed is a yellow solid when hot and turn to white when cold. Substance T may be
A Lead(II) carbonate B Lead(II) nitrate C Zinc carbonate D Zinc nitrate
24. Which of the following substances are most suitable for preparing lead(II) chloride salt?A Lead(II) nitrate solution and sodium chloride solutionB Solid lead(II) sulphate and sodium chloride solutionC Solid lead(II) carbonate and hydrochloric acidD Solid lead(II) oxide and hydrochloric acid
25. The table below shows the observation of the tests carried out on an unknown solution Z.
Experiment Observation Add lead(II) nitrate solution to solution Z. A white precipitate is formed.Pass ammonia gas into solution Z until in excess.
A white precipitate is formed. The precipitate dissolves when ammonia gas is in excess.
Sulphatesalt
Solution formed
Solution formed
Whiteprecipitate
Sulphatesalt
Solution formed
Solutionformed
Whiteprecipitate
The observation shows that Z may be A zinc sulphateB calciun chlorideC magnesium nitrateD aluminium chloride
26. When copper(II) carbonate is heated, it decomposes according to the equation below. CuCO3 → CuO + CO2
What is the mass of copper(II) carbonate used to produce 600 cm3 carbon dioxide gas at room temperature and pressure?[Relative atomic mass: Cu, 64; C, 12; O, 16; 1 mol of gas occupies 24 dm3 at room temperature and pressure]
A 2.3 gB 3.1 gC 6.2 gD 25.0 g
27. Solution E contains three anions. A series of test is carried out on solution E and the results are shown below.
Add dilute Add silver nitric acid nitrate solution
Add barium chloride solution
The ions present in solution E are A nitrate ion, sulphate ion and carbonate ion B sulphate ion, carbonate ion and chloride ion C hydroxide ion, sulphate ion and chloride ion D sulphate ion, hydroxide ion and carbonate ion
28. The reaction between barium chloride solution and sodium carbonate produces an insoluble salt. The salt produced can be dissolved by adding
A sodium hydroxide solutionB potassium chloride solution C aqueous ammoniaD nitric acid
29. The equation below represents the reaction between barium hydroxide and potassium chromate(VI) .
Ba(OH)2 + K2CrO4 → BaCrO4 + 2KOH
Barium hydroxide solution reacts with 10 cm3 of potassium chromate(VI) solution to produce 0.63 g of barium chromate. What is the concentration of potassium chromate solution?
Solution EEffervescence
occurs. A colourless
solution is formed.
Whiteprecipitate
Whiteprecipitate
[Relative atomic mass: O, 16; Cr, 52; Ba, 137]A 0.025 mol dm-3
B 0.05 mol dm-3
C 0.25 mol dm-3
D 0.50 mol dm-3
30. The figure below shows the test on X. X is a mixture of two salts with the same cation.
Add distilled water and filter
+ sodium chloride solution
when heated
Which of the following substances are present in X?A Zinc carbonate and zinc chlorideB Magnesium carbonate and magnesium nitrateC Lead(II) carbonate and lead(II) nitrateD Lead(II) sulphate and lead(II) chloride
31. Which of the following salt is not decomposed by heat?A Zinc nitrateB Lithium nitrateC Potassium carbonateD Lead(II) carbonate
32. 5.0 cm3 lead(II) nitrate solution requires 25.0 cm3 sodium chloride solution 0.2 mol dm-3 to complete the reaction according to the equation below:
Pb2+(aq) + 2Cl-(aq) → PbCl2(s) What is the molarity of lead(II) nitrate solution? A 0.01 mol dm-3
B 0.10 mol dm-3
C 0.20 mol dm-3
D 0.50 mol dm-3
33. Which of the following ions produces a precipitate when sodium sulphate solution is added ? I Al3+ ion II Ca2+ ion III Cu2+ ion IV Pb2+ ion
X
Precipitate
White precipitate
Solution
Precipitate dissolves
A I and III only B II and IV only C I, II and IV only D II, III and IV only
34. The equation below shows the action of heat on the carbonate salt of metal X.
XCO3 → XO + CO2
How many moles of XCO3 are needed to produce 4.0 g of oxide X? [Relative atomic mass: C,12; O, 16; X, 64] A 0.03
B 0.05 C 0.08 D 0.09
35. The diagram below shows the crystalline structure of salt, NaCl. Which of the following is not a characteristic of the crystal of NaCl?
A It has sharp corners. B It has flat surfaces. C It has an acute angle between the two adjacent surfaces. D It has straight edges between two adjacent surfaces.
36 Which of the following ions form a white precipitate that dissolves in excess sodium hydroxide solution?
I Al3+
II Mg2+ III Pb2+
IV Zn2+
A I and II only B II and IV only C I, II and III only D I, III and IV only
37. 3.2 g of copper(II) oxide powder is reacted with excess dilute nitric acid. What is the mass of copper(II) nitrate formed in the reaction?Use the information that the relative atomic mass of N = 14, O = 16 and Cu = 64.
A 3.76 gB 4.96 gC 5.04 gD 7.52 g
38. Gas X is passed into an acidic dichromate solution. The colour of the solution changes from orange to green. What is gas X?
A Sulphur dioxide B Hydrogen chloride
C Nitrogen dioxide D Chlorine
39. The formula for a sulphate ion is SO42- and for a nitrate ion is NO3
-. If the formula of the sulphate salt of M is MSO4, what is the formula of the nitrate salt of M?
A MNO3
B M2NO3
C M(NO3)2
D M(NO3)3
40. 0.12 g of magnesium reacts with excess hydrochloric acid to produce hydrogen gas. [Given that the relative atomic mass of H=1, Mg=24, Cl=35.5 and 1 mol of gas occupies 24 dm3 at room temperature and pressure] Which of the following is true about the reaction?
I Mg + 2H+ → Mg2+ + H2
II Volume of gas released is 120 cm3
III Mass of the salt formed is 0.30 g IV This is a redox reaction
A I and II only B I and III only C I, II and IV only D II, III and IV only
41. Which of the following ions form precipitate that dissolves in excess ammonia solution?
I. Al3+ II. Cu2+III. Pb2+
IV. Zn2+
A. I and II onlyB. II and IV onlyC. I, II and III onlyD. I, III and IV only
42. You are asked by your teacher to verify the cation and anion in a sample of ammonium chloride salt solution, What substance can you use to verify the cation and anion?
Cation AnionA Nessler reagent Dilute nitric acid and silver nitrateB Nessler reagent Dilute hydrochloric acid and barium chlorideC Potassium thiocyanate Dilute nitric acid and silver nitrateD Potassium thiocyanate Dilute hydrochloric acid and barium chloride
Structural question
1. Figure 2 shows a flow chart summarizing the series of changes for a compound T.
Heated up + dilute nitric
acid
Solid T
Solid U is yellow in colour when hot and white in colour when cooled.
(a) What is solid U? [ 1 mark ](b) Name the cation and anion in solid T. [ 2 marks ](c ) (i) Name gas V. [ 1 mark ]
(ii) What is observed when gas V is passed through limewater? [ 1 mark ](iii) Write the chemical equation for reaction between gas T with limewater.
[ 3 marks](d) Write the chemical equation to represent the effect of heat on solid T. [ 1 mark ]
(e) (i) Name solution Y. [ 1 mark ](ii) Describe briefly a chemical test to identify the anion in solution Y.
[ 3 marks ](f) Name the type of reaction which occurs when solid U reacts with dilute hydrochloric acid to form
solution W. [ 1 mark ](g) (i) What are gas Y and gas Z ? [ 2 marks ]
(ii) Write the balance chemical equation for the effect of heat on solution Y.[ 1 mark ]
2. Figure 3 summarises the series of reactions that involves lead compounds.
Lead(II)nitrate Solid J + Mix of gases K and L
Heated up
Figure 3
(a) What is solid J ? [ 1 mark ](b) What is the colour of solid J when hot and cooled ? [ 1 mark ](c ) Write a balance chemical equation to represent the effect of heat on lead(II) nitrate to form solid J and a
mixture of gas K and N. [ 3 marks ](d) (i) Name precipitate M. [ 1 mark ]
(ii) State a way to test compound M. [ 1 mark ](iii) Write the ionic equation to show then formation of precipitate M.
[ 1 mark ](e) Sodium hydroxide solution is added little by little into solution N until there is no more change. What can be
observed ? [ 1 mark ](f) How can you obtain dry crystal salt, N , from solution N ? [ 3 marks ](g) A piece of zinc is put into solution N.
(i) Predict the observation. [ 1 mark ](ii) Write the chemical equation to represent the reaction which has occurred.
[ 1 mark ]
White precipitate M Solution N
Add dilute hydrochloric
acid
Add dilute nitricacid
Compound J Gas K[Brown colour and acidified]
+
Gas L[Colourless]
+
Heat
Figure 3
3. Figure 3 shows a series of process done by a student to identify a compound J.
(a) With refer to reaction I, white precipitate Q is formed which is soluble in excess sodium hydroxide solution. Name all the ions which are probably presence in solution J.
[ 1 mark ]
(b) Referring to reaction I and II, name the cation presence in solution J.[ 1 mark ]
(c ) Write down the ionic equation for the reaction forming the white precipitate, R.[ 3 marks ]
(d) (i) Name two cations which produced white precipitate that will not dissolve in excess sodium hydroxide solution. [ 1 mark ]
(ii) State one confirmatory test for one cation presence in (d)(i). [ 3 marks ]
Essay questions1. (a) What is the meaning of salt ? [ 1 mark ]
(b) (i) State four types of preparation reaction for insoluble iron(II) chloride. [ 4 marks ]
(ii) For each type of reaction in (b)(i), write a chemical equation for salts prepared through the reactions mentioned. [ 4 marks ]
Gas K[Brown colour and acidified]
+
Gas L[Colourless]
+
Dissolved inwater
Colourless J solution
White precipitate R
Reaction II
+ Na2SO4 (aq)
White precipitate Q Dissolved in
excess sodium hydroxide solution
Reaction I
+ NaOH (aq)
(c ) You are required to prepare zinc sulphate salt. Chemical compounds provided are listed as follows:
Describe a laboratory experiment how you can prepare zinc sulphate salt that is dry. In your description, include the chemical equations involved.
[ 11 marks ]
2. (a) What is meant by precipitation reaction ? [ 1 mark ](b) Describe how you can use ammonia solution to differentiate the
following solutions.
(c ) A solution contains iron(II) ion cation. Decribe briefly three laboratory experiment for you to confirm the presence of iron(II) ion in the solutions.
[ 6 marks ](d) Describe a laboratory experiment to prepare lead(II) nitrate crystal salt in the laboratory. In your
description, write the chemical equations for the reactions involved.[ 9 marks ]
3 .(a) The following information is about hydrochloric acid and ethanoic acid.* the pH of 1 mol dm-3 hydrochloric acid is 1* the pH of 1 mol dm-3 ethanoic acid is 4
[4 marks]Explain why these two solution have different pH values(b) Two bottles of reagent each containing hydrochloric acid and ammonium chloride solution.
Qualitative analysis can be used to determine the presence of cations and anions in solutions.Describe chemical tests that can be used to verify the ions in each solution.
[10 marks]© The chemical equation of reaction P is as follows:
CuCl2 + Na2CO3 2NaCl + CuCO3
Excess sodium carbonate is added to 50cm3 of 0.5 mol dm-3 copper(II) chloride. Given that the relative molecular mass of CuCO3 = 124. Calculate the mass of copper(II) carbonate precipitate formed.
[2 marks] (d) When copper(II) carbonate is heated, it produces solid X and gas Y.
(i) Name solid X and state its colour. [2 marks]
(ii) Name gas Y and describe a method to verify its identity. [2 marks]
Dilute sulphuric acid Sodium carbonate solution Zinc nitrate solution
Potassium nitrate solution Zinc sulphate solution Magnesium chloride solution