LABORATORY PRACTICALS _ CHEMISTRY
NECTA 2015
2. You are provided with the following:
U: A solution containing 79g of Na2S2O3.5H2O
V: A solution contain 0.1mol/dm-1 of dilute HCL
T: Distilled water
Stop watch/clock
Procedure
(i) Place a 100cm3 beaker on top of letter X on a plain paper provided
(ii) Measure 8.0cm3 of U and 2cm3 of T and put them in the beaker in (i)
(iii) Measure 10cm3 of V and put it into a beaker containing U and T; immediately start the stop watch and observe the changes from above
(iv) Record the time taken for the disappearance of letter X
(v) Repeat steps (i) to (iv) using the data shown in table 1.
Table 1
Number of experiment
|
Volume of U(cm3)
|
Volume of V(cm3)
|
Volume of T(cm3)
|
Time (t) in second
|
1/t(sec-1)
|
1
|
8
|
10
|
2
| ||
2
|
6
|
10
|
4
| ||
3
|
4
|
10
|
6
| ||
4
|
2
|
10
|
8
| ||
5
|
1
|
10
|
9
|
Questions:
a) What is the aim of the whole experiment
b) Complete table 1
c) Give reasons (s), identify the experiment in which the reaction was
i. Fast
ii. Slow
d) With state symbols write balanced chemical equation for the reaction between U and V
e) List four factors which can affect rate of chemical reaction
f) Write the electronic configuration of the production which causes the solution to cloud letter X
g) What can you conclude from the data obtain
SOLUTION
a) The aim of the whole experiment is to show the effect of concentration on the rate of chemical reaction.
b) Table of results
Table 1
Number of experiment
|
Volume of U(cm3)
|
Volume of V(cm3)
|
Volume of T(cm3)
|
Time (t) in second
|
1/t(sec-1)
|
1
|
8
|
10
|
2
|
21.12
|
0.047
|
2
|
6
|
10
|
4
|
28.62
|
0.035
|
3
|
4
|
10
|
6
|
44.78
|
0.022
|
4
|
2
|
10
|
8
|
102.31
|
0.010
|
5
|
1
|
10
|
9
|
295.65
|
0.003
|
C)
i. The experiment in which the reaction was fast was experiment number 1 because it has higher concentration and the time taken for disappearance of letter X was the shortest compared to others.
ii. The experiment in which the reaction was slow was experiment number 5 because it has lower concentration and the time taken for disappearance of letter X was the longest compared to others.
d)
2HCl (aq) + Na2S2O3(aq) 2NaCl (aq) + H2O(L) + SO2(g) + S(s)
e)
i/ Concentration
ii/ Temperature
iii/ Pressure
iv/ Catalyst
f) The electronic configuration of the product which cause the solution to cloud letter X , the product was Sulphur (S) and its electronic configuration = 2:8:6
g) Conclusion
As concentration decreases, the times taken for the disappearance of letter X increases. Or concentration is inversely proportional to the time but the concentration is directly proportional to the rate of reaction.
NECTA 2016
2. You are provided with the following:
BB: A solution containing 79g of Na2S2O3.5H2O
DD: A solution contain 0.1mol/dm-1 of dilute HCL
A stop watch/ clock; a white plain paper with a cross and thermometer
Procedure
(i) Place a 100cm3 beaker on top of a cross on a plain paper provided such that the cross is visible through the solution when viewed from above
(ii) Prepare a water bath using a 250 cm3 or 300 cm3 beaker
(iii) Measure exactly 10cm3 of BB and 10 cm3 of DD pour into separate boiling test tubes
(iv) Put the two boiling test tubes into the water bath in (ii) above and warm the contents to 400C.
(v)Immediately pour the hot solutions BB and DD into the 100 cm3 beaker in (i) above and simultaneous start the stop watch/clock. Record the time taken in seconds, for the cross to disappear completely.
(vi) Repeat procedures (iii) to (v) at different temperature, 500C, 600C and 700C. Record your reading in a tabular form as shown in table 1.
Table 1
Temperature
|
Time (sec)
|
1/time (sec)
|
40
| ||
50
| ||
60
| ||
70
|
Questions
a. (i) Record the room temperature
(ii) Complete the table by filling the blank columns
b. Plot a graph of temperature against time from your results
c. Write a balanced ionic equation for the reaction between the dilute acid and sodium thiosulphate
d. What does 1/time represernt?
e. From obtained data what can you conclude the effect increasing temperature on the rate of chemical reaction?
SOLUTION
a. (i) Room temperature = 210C
(ii) Table of results
Temperature
|
Time (sec)
|
1/time (sec)
|
40
|
17.22
|
0.06
|
50
|
10.03
|
0.10
|
60
|
6.47
|
0.15
|
70
|
3.62
|
0.28
|
b. The graph of temperature against time
C. Na2S2O3 (aq) + 2HCl (aq) 2NaCl (aq) + H2O (L) + SO2 (g) + S (s)
In ionic equation
2Na+ + S2O32- + 2H+ + 2Cl- 2Na+ + 2Cl- + H2O(L) + SO2(g) + S(s)
S2O32- + 2H+ H2O (L) + SO2 (g) + S (s)
d. 1/time represent rate of chemical reaction
e. As temperature of the reactants increases, the rate of chemical reaction is increases Or temperature is directly proportional to the rate of chemical reaction.
NECTA 2017
2. You are provided with the following:
E: A solution containing 79g of Na2S2O3.5H2O
F: A solution contain 0.1mol/dm-1 of dilute HCL
G: Distilled water
A stop watch/ clock; a white plain paper and thermometer.
Procedure
(i) Put a beaker (100cm3) on top of a cross on the given sheet of paper.
(ii) Measure 25 cm3 of E using measuring cylinder and pour into a beaker in (i).
(iii) Using another measuring cylinder measure 5 cm3 of F and pour it into a beaker containing E and instantly, start a stop watch.
(iv) Stir the mixture with a glass rod while you keep on observing the cross from above; record the time taken for the cross to disappear.
(v) Repeat the procedures for different concentrations of E by taking 20 cm3, 15 cm3, 10 cm3 and 5 cm3 of the original E and making the total volume up to 25 cm3 by adding G.
Repeat the results as shown in the table 1.
Table 1
Volume of E (cm3)
|
Volume of G (cm3)
|
Time taken for the cross to disappear (sec)
|
25
| ||
20
| ||
15
| ||
10
| ||
5
|
Questions
a) Complete filling the Table 1
b) 
(i) Using the data in the table, plot a volume time graph (volume on the y-axis and time in second on the x-axis)
(i) Using the data in the table, plot a volume time graph (volume on the y-axis and time in second on the x-axis)
(ii) What does the shape of the graph indicate?
c) Write down the ionic equation of the reaction between E and F.
d) Why did the cross disappear?
e) Write two uses of the product which obscured the cross.
SOLUTION
a)
Volume of E (cm3)
|
Volume of G (cm3)
|
Time taken for the cross to disappear (sec)
|
25
|
0
|
27.27
|
20
|
5
|
39.94
|
15
|
10
|
52.10
|
10
|
15
|
65.40
|
5
|
20
|
140.00
|
b) (i) The shape of the graph is a curve
c)
. Na2S2O3 (aq) + 2HNO3 (aq) 2NaNO3(aq) + H2O (L) + SO2 (g) + S (s)
In ionic equation
2Na+ (aq) + S2O32- (aq) + 2H+ (aq) + 2NO3- (aq) 2Na+ + 2NO3- + H2O (L) + SO2 (g) + S(s)
S2O32- (aq) + 2H+(aq) H2O (L) + SO2 (g) + S (s)
d) Cross disappear because of Sulphur (S) or Precipitation of sulphur or sulphur deposite
e)
1. Sulphur is used in the manufacture of carbon disulphate, sodium thiosulphate, gun powder, matches and in fireworks.
2. Sulphur is used on vulcanization of rubber. Natural rubber is soft and sticky. Heating it with sulphur makes it hard non-sticky and more elastic. This process of heating of natural rubber with sulphur is known as vulcanization.
3. Sulphur is used for medicine.
It is used for its cleansing properties in the treatment of infections.
1. Sulphur is used in the manufacture of carbon disulphate, sodium thiosulphate, gun powder, matches and in fireworks.
2. Sulphur is used on vulcanization of rubber. Natural rubber is soft and sticky. Heating it with sulphur makes it hard non-sticky and more elastic. This process of heating of natural rubber with sulphur is known as vulcanization.
3. Sulphur is used for medicine.
It is used for its cleansing properties in the treatment of infections.
4. Sulphur is used for skin care or curing skin diseases.
5. Sulphur is used for give specific shapes to the hair.
6. Sulphur is used for agriculture
Sulphur is necessary for the growth and development of plant life used in fertilizers
NECTA 2018
2. You are provided with the following:
H1: A solution of 0.25 mol/dm-3 Na2S2O3;
H2: A solution of 2M HCL;
Distilled water; stop watch; Thermometer and a plain paper marked X.
Procedure
Place 150cm3 of water in the 250cm3 beaker and use this as your water bath; heat the water 800C. Measure 10cm3 of H1 and 25cm3 of water and pour the cotents into the 100cm3 beaker. Put the beaker with the contents ito a hot water bath. When the contents attain a temperature of 700C, place the beaker on top of the marker X on the paper provided. Add 10cm3 of H2 and immediately start the stop watch. Swirl the beaker twice and look vertically on the top of the beaker so as to see X through the bottomof the beaker. Stop thr clock when X is invisible. Record the time taken for X to disapper completely. Repeat the experiment at different temperatures as shown in the table 1.
Table 1
Exp. No.
|
Temperature of H1
(0C)
|
Time (sec)
|
Rate 1/ t (S-1)
|
1
|
70
| ||
2
|
60
| ||
3
|
50
| ||
4
|
40
| ||
5
|
Room temperature
|
QUESTIONS
a) Fill Table 1.
b) Write a balance equation for reaction between H1 and H2
c) Which product causes the solution to cloud the letter X?
d) Plot a graph of rate (1/t) against temperature
e) What conclusion can you draw from this experiment?
SOLUTION
a)
Table 1
Exp. No.
|
Temperature of H1
(0C)
|
Time (sec)
|
Rate 1/ t (S-1)
|
1
|
70
|
2.56
|
0.39
|
2
|
60
|
4.05
|
0.25
|
3
|
50
|
9.23
|
0.11
|
4
|
40
|
14.08
|
0.07
|
5
|
30
|
29.15
|
0.03
|
b) 
2HCl (aq) + Na2S2O3(aq) 2NaCl (aq) + H2O(L) + SO2(g) + S(s)
2HCl (aq) + Na2S2O3(aq) 2NaCl (aq) + H2O(L) + SO2(g) + S(s)
c) The product which causes the solution to cloud the letter X was Sulphur (S)
d) The graph of rate (1/t) against temperature
e) conclusion
As temperature of the reactant decreases the time taken for letter X to disappear increases or temperature is inversely proportional to the time but the graph was increase.
TECHNIC QUESTION
2. You are provided with the following:
Z: A solution containing 32.24g/dm3 of Na2S2O3.5H2O
U: A solution contain 2 M HCL
Distilled water
Stop watch/clock
Procedure
(i) Mark letter A on a piece of paper with black ink
(ii) Measure 50 cm3 of Z and pour it into a conical flask
(iii) Measure 10cm3 of U by using different measuring cylinder immediately start the stop watch and observe the changes from above
(iv) Stand the conical flask on the paper above the cross. Look down vertically through the mouth of the conical flask and make sure you can see the cros at the bottom of the flask.
(v) Swirl the flask while keep on observing until the letter A disappears
(vi) Record the time taken for the disappearance of letter A
(vii) Repeat the whole procedure using 40 cm3, 30 cm3, 20 cm3 and finally 10 cm3.
Table 1
Number of experiment
|
Volume of Z (cm3)
|
Volume of distilled H2O (cm3)
|
Volume of Na2S2O3after addind water (mol/dm3)
|
Time (t) in second
|
Rate of reaction(S-1)
|
1
|
50
|
0
| |||
2
|
40
|
10
| |||
3
|
30
|
20
| |||
4
|
20
|
30
| |||
5
|
10
|
40
|
Questions
a) Complete filling the table of results showing your working for the fifth column (conc. In mol/dm3)
b) Write the balance chemical equation between Z and U
c) Plot the graph of time (y-axis) against Concentration of Na2S2O3 (x- axis)
d) What substance was produced during the reaction which obscured the mark A
e) What conclusion can you draw from the result of this experiments
f) Briefly explain the smell and color observed as the reaction take place
g) Explain how concentration changes affect the rate of chemical reaction
SOLUTION
a) Table of results
Number of experiment
|
Volume of Z (cm3)
|
Volume of distilled H2O (cm3)
|
Volume of Na2S2O3after adding water (mol/dm3)
|
Time (t) in second
|
Rate of reaction(S-1)
|
1
|
50
|
50
|
0.13
|
10.22
|
0.10
|
2
|
40
|
50
|
0.104
|
13.63
|
0.07
|
3
|
30
|
50
|
0.078
|
17.22
|
0.06
|
4
|
20
|
50
|
0.052
|
25.34
|
0.04
|
5
|
10
|
50
|
0.026
|
55.50
|
0.02
|
Molarity = Concentration g/dm3
Molar mass
Molarity = 32.24g/dm3
248. 17g/mol
Molarity = 0.13mol/dm3
Experiment 1
0.13 x 50 = 6.5
6.5 ÷ 50 = 0.13
Experiment 2
0.13 x 40 = 5.2
5.2 ÷ 50 = 0.104
Experiment 3
0.13 x 30 = 3.9
3.9 ÷ 50 = 0.078
Experiment 4
0.13 x 20 = 2.6
2.6 ÷ 50 = 0.052
Experiment 5
0.13 x 10 = 1.3
1.3 ÷ 50 = 0.026
b)
Na2S2O3(aq + 2HCl (aq) 2NaCl (aq) + H2O(L) + SO2(g) + S(s)
c) The graph of time (y-axis) against Concentration of Na2S2O3 (x- axis)
d) Substance that was produced during the reaction which obscured the mark A was Sulphur (S) (precipitation of sulphur)
e) Conclusion
As concentration of sodium thiosulphate decreases the time taken for disappearance of letter A increases.
f) The smell or irritating chocking smell produced the production of Sulphur dioxide (SO2)
g) Increase in concentration of sodium thiosulphate increases the rate of chemical reaction or concentration is directly proportional to the rate of chemical reaction.
3. QUALITATIVE ANALYSIS
3. Sample F is a simple salt contain one cation and one anion. Carefully carry out the experiments described below and record all your observations, inferences and hence identify the cation and anion present sample salt F.
S/N
|
Experiment
|
Observation
|
Inference
|
(a) i/ The cation present in sample F is………….
ii/ The anion present in sample F is………….
(b) Write the chemical formula of sample F……………
(c) Write the name of sample F ……………..
SOLUTION
S/N
|
Experiment
|
Observation
|
Inference
|
1
|
Appearance of sample F
|
White powder salt
|
NH4+, Na+, Ca2+, Zn2+, Pb2+ May be present.
Or
Transition metals Fe2+,Fe3+,Cu2+ may be absent.
|
2
|
Action of heat
|
Colourless gas evolves, which turn lime water milk and wet litmus paper from blue to red
|
CO32+,HCO3-May be present
|
3
|
Action of dilute HCl acid on a solid sample
|
Effervescence of colourless gas evolves, which turns lime water milky and wet litmus paper from blue to red
|
CO32-,HCO3-May be present
|
4
|
Action of concentrated H2SO4 on a solid sample
|
Effervescence of colourless gas evolves. The gas turns lime water milky and wet litmus paper from blue to red
|
CO32-,HCO3-May be presen
|
5
|
Flame test
|
Golden yellow flame
|
Na+ May be present
|
6
|
Solubility of solid samples
|
Soluble forming colourless solution
|
CO32-, HC03-, of Na+, NH4+ May be present
|
7
|
Action of NaOH solution on a sample solution
|
No precipitate is formed, even on warming
|
Na+ May be present
|
8
|
Action of NH3 solution on a sample solution
|
No precipitate is formed
|
Ca2+, Na+, NH4+ May be present
|
9
|
Confirmatory test for CO32-
|
White precipitate is formed before warming the contents
|
CO32-Confirmed
|
(a) i/ The cation present in sample F is Na+
ii/ The anion present in sample F is CO32-
(b) The chemical formula of sample F is Na2CO3
(c) The name of sample F is Sodium carbonate
NECTA 2015
3. Sample M contains one cation and one anion. Using systematic qualitative analysis procedures carry out the experiment and record carefully your observations, inferences and finally identify the cation and anion present sample M. Record your work in a tabular form as shown in Table 2.
Table 2
S/N
|
Experiment
|
Observation
|
Inference
|
Conclusion
(i) 
The cation sample M is
The cation sample M is
(ii) 
The anion sample M is
The anion sample M is 
(iii)The chemical formula of sample M is
SOLUTION
S/N
|
Experiment
|
Observation
|
Inference
|
1
|
Appearance of sample M
|
White crystalline salt
|
NH4+, Na+, Ca2+, Zn2+, Pb2+ May be present.
Or
Transition metals Fe2+,Fe3+,Cu2+ may be absent.
|
2
|
Action of heat
|
Cracking sound with brown gas
|
NO3- of Pb2+ May be present
|
3
|
Action of dilute HCl acid on a solid sample
|
Effervescence of colourless gas evolves, which turns lime water milky
|
CO32-,HCO3-May be present
|
4
|
Action of concentrated H2SO4 on a solid sample
|
Evolution of brown fumes, which turn wet litmus paper from blue to red
|
NO3- May be presen
|
5
|
Flame test
|
Blue-white (pale-blue) flame
|
Pb2+ May be present
|
6
|
Solubility of solid samples
|
Insoluble in cold water but soluble in hot water
|
Cl- of Pb2+ May be present
|
7
|
Action of NaOH solution on a sample solution
|
White precipitate is formed, soluble in excess
|
Zn2+, Pb2+ May be present
|
8
|
Action of NH3 solution on a sample solution
|
White precipitate is formed, insoluble in excess
|
Pb2+ May be present
|
9
|
Confirmatory test for NO3-
|
Brown rng is formed at the junction of the liquids
|
NO3- Confirmed
|
10
|
Confirmatory test for Pb2+
|
Yellow precipitate which disappears on warming but re-appears on cooling
|
Pb2+ Confirmed
|
Conclusion
(i) The cation sample M is Pb2+
The cation sample M is Pb2+
(ii) The anion sample M is NO3-
The anion sample M is NO3-
(iii)The chemical formula of sample M is Pb(NO3)2
FOREXAMPLE OF GUIDED QUESTIONS
NECTA 2016
3. You are provided sample R containing one cation and one anion. Carryvout the guided systematic procedure in the table 2 to identify the cation and anion present in the sample R.
Table 2
S/n
|
Experiments
|
Observation
|
Inference
|
(a)
|
Observe sample R
| ||
(b)
|
Heat sample R in a dry test tube
| ||
(c)
|
Prepare a stock solution of sample R. Devide the resulting solution into six portions then add:
| ||
(i) dilute HCl solution in small quantities then in excess to the first portion
| |||
(ii) Small amount of concentration H2SO4 to the second portion, then warm
| |||
(iii) NaOH solution to the third portion, drop wise till excess
| |||
(iv) dilute NH4OH in small amount then in excess to the fourth portion
| |||
(v) FeSO4 solution followed by Conc.H2SO4 to the fifth portion
| |||
(vi) KI solution to the sixth portion, warm then cool the mixture.
|
Conclusion
(i) The cation sample R is .
The cation sample R is .
(ii) The anion sample R is .
The anion sample R is .
(iii)The chemical formula of sample R is .
(iv) Write the equestions for the reactions that took place at experiments (b) and (c) (ii).
SOLUTION
S/n
|
Observation
|
Inference
|
(a)
|
White crystalline salt
|
NH4+, Na+, Ca2+, Zn2+, Pb2+ May be present.
Or
Transition metals Fe2+,Fe3+,Cu2+ May be absent.
|
(b)
|
Cracking sound with brown gas
|
NO3- of Pb2+ May be present
|
(c)
(i)
|
Insoluble in cold water but soluble in hot water
|
Cl- of Pb2+ May be present
|
Effervescence of colourless gas evolves, which turns lime water milky
|
CO32-,HCO3- May be present
| |
(ii)
|
Evolution of brown fumes, which turn wet litmus paper from blue to red
|
NO3- May be presen
|
(iii)
|
White precipitate is formed, soluble in excess
|
Zn2+, Pb2+ May be present
|
(iv)
|
White precipitate is formed, insoluble in excess
|
Pb2+ May be present
|
(v)
|
Brown rng is formed at the junction of the liquids
|
NO3- Confirmed
|
(vi)
|
Yellow precipitate which disappears on warming but re-appears on cooling
|
Pb2+ Confirmed
|
Conclusion
(i) The cation of sample R is Pb2+
The cation of sample R is Pb2+
(ii) The anion of sample R is NO3-
The anion of sample R is NO3-
(iii)The chemical formula of sample R is Pb(NO3)2
(iv) PbNO3 (aq) + H2SO4 (aq) PbSO4 (aq) + NO2 (g) + H2O (L)
NECTA 2017
3. Sample Q is a simple salt containing one cation and one anion. Carefully carry out all the experiments described in the Table 2. Record all your observation and appropriate inferences to identify the ions present in sample Q.
Table 2
S/n
|
Experiments
|
Observation
|
Inference
|
(a)
|
Observe sample Q
| ||
(b)
|
Put a spatulaful of sample Q in a test tube and add distilled water.
| ||
(c)
|
Transfer 0.5g of sample Q in a test tube, add dilute HCl
| ||
(d)
|
Transfer 0.5g of sample Q in a test tube, add concentrated sulphuric acid.
| ||
   (e) |
Dissolve sample Q then divide the resulting solution into three portions.
(i) To the first portion add sodium hydroxide solution.
| ||
(ii) To the second portion add ammonia solution
| |||
(iii) To the third portion add potassium ferricyanide solution [K3Fe(CN)6].
| |||
(iv) To the fourth portion add lead acetate solution followed by acetic acid solution.
|
Conclusion
(a) 
(i) The cation sample Q is
(i) The cation sample Q is
(ii) The anion sample Q is 
(iii)The Compound Q is
(b) Write the reaction equation that took place at experiments (c)
(c) State three chemical properties of metal in Q
(d) State two uses of Q
SOLUTION
S/n
|
Observation
|
Inference
|
(a)
|
Pale or light green
|
Fe2+ May be present.
|
(b)
|
Insoluble
|
CO32- of Ca2+, Pb2+ , Zn2+, Fe2+, Fe3+ , Cu2+ May be present
|
SO42-, of Ca2+, Pb2+ May be present
| ||
(c)
|
Effervescence of colourless gas evolves, which turns lime water milky
|
CO32-,HCO3- May be present
|
(d)
|
No gas evolves
|
SO42- May be present
|
(e)
(i)
|
Green precipitate is formed, insoluble in excess, which turns brown on standing
|
Fe2+ May be presen
|
(ii)
|
Green precipitate is formed, insoluble in excess
|
Fe2+ May be present
|
(iii)
|
Deep blue precipitate
|
Fe2+ Confirmed
|
(iv)
|
White precipitate insoluble
|
SO42- Confirmed
|
Conclusion
(a) (i) The cation sample Q is Fe2+
(i) The cation sample Q is Fe2+(ii) The anion sample Q is SO42-
(iii)The Compound Q is FeSO4
H+ + Cl- HCl (aq)
(c) Three chemical properties of iron (Fe)
i/ Iron combines easily with oxygen to produce rust.
ii/ Iron both malleable it can be shaped into thin wires or sheets
iii/ Iron has a high tensile strength so it can be stretched without breaking
iv/ Iron dissolves in dilute acids
(d) Two uses of iron (Fe)
i/ Making steel
ii/Agriculture
iii/ Food and medicine
NECTA 2018
3. Sample N is a simple salt containing one cation and one anion. Carefully carry out all the experiments described in the Table 2. Record all your observations and appropriate inferences to identify the cation and anion present in sample N.
Table 2
S/n
|
Experiments
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Observation
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Inference
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(a)
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Appearance of the solid sample N
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(b)
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Put a spatulaful of sample N in a test tube and heat.
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(c)
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Add dilute hydrochloric acid to the solid sample N
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(d)
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Perform flame test on the sample.
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| (e) |
Dissolve the sample in water. Divide the resulting solution into two portions:
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(i) Add sodium hydroxide solution to the first portion.
| |||
(ii) Add few drops of magnesium sulphate solution to the second portion, then warm.
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Conclusion
(i) The cation is and the anion is .
(ii) The sample N is .
(iii) Write chemical equations (with state symbols) to show reactions which took place in the experiments (b) and (c).
(iv) Describe three uses of sample N
SOLUTION
S/N
|
Observation
|
Inference
|
(a)
|
White powder salt
|
Or
Transition metals Fe2+,Fe3+,Cu2+ may be absent.
|
(b)
|
Colourless gas evolves, which turn lime water milk and wet litmus paper from blue to red
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CO32+,HCO3- May be present
|
(c)
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Effervescence of colourless gas evolves, which turns lime water milky and wet litmus paper from blue to red
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CO32-,HCO3- May be present
|
(d)
|
Golden yellow flame
|
Na+ May be present
|
(e)
|
Soluble forming colourless solution
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CO32-, HC03-, of Na+, NH4+ May be present
|
(i)
|
No precipitate is formed, even on warming
|
Na+ May be present
|
(ii)
|
White precipitate is formed before warming the contents
|
CO32- Confirmed
|
Conclusion
(i) The cation is Na+ and the anion is CO32-
(ii) The sample N is Sodium carbonate (Na2CO3)
(iii) 
Na2CO3 (aq) + 2HCl (aq) 2NaCl (aq) + H2O (L) + CO2 (g)
Na2CO3 (aq) + 2HCl (aq) 2NaCl (aq) + H2O (L) + CO2 (g)
(iv) Three uses of Sodium Carbonate
i/ Manufacturing of glass and production of chemicals: Sodium carbonate reduces the amount of energy required for the production of glass and reduces the cost of manufacture.
ii/ It can remove alcohol and grease stains from clothing, coffee pots.
iii/ Used in medicine principally for its acid neutralizing.
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