NECO Chemistry Practical Questions and Answers | –Download PDF.

NECO Chemistry Practical Questions and Answers | –Download PDF. The National Examination Council of Nigeria (NECO) Examination is around the corner. This article provides the readers with the information on how to download NECO Chemistry Practical Questions and Answers. NECO Mathematics Questions are essential for you to know if you want to pass the NECO SSCE Mathematics Exams 2023.

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NECO Chemistry Practical Sample Questions and Answers 2023

NECO Practical Chemistry Answers 2023 Loading…

Today’s Chemistry Practical Answers:

(1a)

Tabulate

Volume of pipette used=25cm3.

Indicator used= Methyl orange

Under Titration, Rough, 1st, 2nd, 3rd,

Final burette reading; |25.00| |23.40| |23.50| 23.60|

Initial burette reading; |0.00| |0.00| |0.00| |0.00|

Volume of A used; |25.00| |23.40| |23.50| |23.60|

(1ai)

Average volume of Acid used=23.40+23.50+23.60/3 =70.5/3=23.50cm3

(1aii)

This is because it is a reaction between a weak acid and strong base

(1aiii)

A funnel should be used while transferring the acid into the burette.

(1bi)

Conc of A in mol|dm³ =?

Conc of A in g|dm³ = 12.75g|dm³

Molar mass of A, NaHSO⁴ = 23+1+32+64

=120g|dm³

From.

Conc(mol/dm³) = conc(g/dm³)/molar mass

Conc =12.75/120

Conc =0.106mol/dm³

(1bii)

Con of B in mol/dm³ =?

Ca =0.106, Cb =? Va =23.50cm³, Vb =25.00cm³

na=1 , nb=1

From; CaVa/CbVb=na/nb

Cb=CaVanb/Vbna

Cb=0.10623501/25.001

Cb=2.5/25

Cb=0.1mol/dm³

(1biii)

Conc of B in g/dm³=?

Molar mass of B , NaOH=23+16+1=40g/mol

From; conc(g/dm³)=conc(mol/dm³)molar mass

=0.140

=4.0g/dm³

(1biv)

Mass of salt formed =?

Recall mole of NaHSO⁴=?

From; mole =con(mol/dm³)*vol(cm³)/1000

Mole=0.106*23.50/1000

Mole=0.0025mol of NaHSO⁴

By proportion 1mol of NaHSO⁴ produce 1mol of Na²SO⁴ 0.0025mol of NaHSO⁴ will produce X mol of Na²SO⁴ X=0.00251=0.0025mol of NaSO⁴

Molar mass of Na²SO⁴=(232) + 32 + (16*4)

=46+32+64

=142g/mol

Recall; mole =mole/molar mass

Mass =mole * molar mass

Mass =0.0025*142

Mass =0.36g of Na²SO⁴

===================================================

(2a)

[PLEASE PUT IN A TABULAR FORM]

TEST

C + 5cm³ of distilled water

OBSERVATION

It dissolve completely

INTERFERENCE

C is a soluble salt

(2bi)

TEST

Solution + NaOH + Heat

OBSERVATION

Effervescence occurs in which a colourless gas with pungent smell and turns red litmus paper to blue is given off.

INFERENCES

NH³ gas from NH⁴+ is present

(2bii)

TEST

Stirring rod of HCL + gas given off

OBSERVATION

a gas which gives a pop sound is given off

INFERENCES

H² is present

(2ci)

TEST

Solution C + drops of BaCL²

OBSERVATION

a white precipitate is formed

INFERENCES

CO²^-3, SO²^-4, SO²^-3, May be present.

(2cii)

TEST

Solution in C(i) + dil HCL

OBSERVATION

the white precipitate dissolve is dil HCL and effervescence occurs in which a colourless and odourless gas which turns blue litmus red and lime water milky is given off

INTERFERENCE

CO² gas from CO²^3- confirmed

===================================================

(3a)

(i)Ca²+

(ii)Pb²+

(3bi)

concentrated acid can be defined as an acid formed when a large quantity of an acid dissolve in a small or little volume of water.

(3bii)

A strong acid is defined as a type of acid that ionize completely in a solution

(3c)

Activated charcoal is used as an adsorbent material

(3d)

(i)Reddish – Brown

(ii) I – red, II – brown.

————————————————

NECO Chemistry Specimen 2023

CHEMISTRY PRACTICAL SPECIMEN:

Requirements:
(a) One burette (50cm³)
(b) One pippete (20cm³/25cm³). However, all
candidates in a center must use pipettes of the
same volume.
(c) The usual apparatus and reagents for
qualitative work including:
(i) Dilute sodium hydroxide solution
(ii) Dilute ammonia solution
(iii) Dilute hydrochloric acid
(iv) Barium chloride solution
(v) Distilled water
(vi) Red and Blue litmus paper
(vii) Phenolphtalein
(d) Methyl orange
(e) One boiling tube
(f) Five test tubes
(g) Filtration apparatus
(h) Source of heat
Each candidate should be supplied with the
following: Labelled An, Bn, Cn, where ‘n’ is the
candidate’s serial number.
(a) 150cm³ of chloride acid solution in a bottle
labelled “An”. The acid solution which should
be the same for all candidates will contain
3.4cm³ of the concentrated hydrochloric acid
per dm³ solution.
(b) 150cm³ of sodium hydroxide solution in a
bottle labelled “Bn”. The solution which should
be the same for all candidates will contain
4.0g of sodium hydroxide per dm³ of solution.
(c) One spatulaful of copper (ii)
tetraoxosulphate (vi) salt in a specimen bottle
labelled “Cn”.

The questions below are strictly for practice not the 2023 Chemistry expo.

All your burette readings (initials and final) as well as the size of your pipette must be recorded but no account of experimented procedure is required. All calculations must be done in your booklet.

1. A is O.200 moldm³ of HCI. C is a solution containing 14/3_g of Na₂CO₃. x H₂O in 500 cm³ of solution. (a) Put A into the burette and titrate it against 20.0 cm³ or 25.0 cm³ portions of C using methyl orange as indicator. Repeat the titration to obtain Consistent titre values. Tabulate your results and calculate the average volume of A used. The equation for the reaction is: Na₂CO₃ x H₂O + 2HCL_(aq) → 2NaCI_(aq) + CO2_(g) + (x+1) H₂O_(I).

(b) From your results and the information provided. Calculate the: (i) concentration of C in moldm^-3; (ii) concentration of C in gdm^-3; (iii) molar mass of Na₂CO₃, xH₂O; (iv) the value of x in Na₂CO₃ xH2O. [H = 1.0; C=12.0; O = 16.0; Na =23.0]

Credit will be given for strict adherence to the instruction, for observations precisely recorded and for accurate inferences. All tests, observations and influences must be clearly entered in the booklet in ink at the same time they are made.

2. F is a mixture to two inorganic salts. Carry out the following exercise on F. record your observation and identify any gas(s) evolved. State the conclusions you draw from the result of each test. (a) Put all of F in a beaker and add about 10cm³ of distilled water. Stir well and filter. Keep the filtrate and the residue. (b)(i) To about 2cm³ of the filtrate, add NaOH_(aq) in drops and then in excess (ii) To another 2cm³ portion of the solution, add a few drops of NHO_3(aq)followed by few drops of AgNO_3(aq). (d)(i) Put all the residue into a clean test-tube and add NHO_3(aq) followed by few solution from 2(d)(i) add NaOH_(aq) in drops and then in excess.

3. State what would be observed if the following reactions are carried out in the laboratory: (i) methyl orange is dropped into a solution of lime juice (ii) hydrogen sulphide gas is bubbled through iron (III) chloride solution; (iii) sulphur (IV) oxide gas is bubbled into acidified solution of KMnO4; (iv) ethanoic acid is added to a solution of K₂CO₃.

CHEMISTRY PRACTICALS ANSWERS

1. Indicator                                 =          Methyl Orange

Volume of the base used        =          25.00cm³

Titration	Rough Titre	1st Titre	2nd Titre	3rd Titre
Final Burette readings cm3	24.70	24.80	24.70	24.90
Initial Burette reading cm3	0.00	0.00	0.00	0.00
Volume of acid used cm3	24.70	24.80	24.90	24.90

Average Titre              =          1^st + 2^nd + 3^rd/3

=          24.80 + 24.70 + 24.90/3

=          24.80cm³

Alternatively 2 concordant titres can be used to calculate average titre.

Equation of the reaction: Na₂CO₃ XH₂O + 2HCI_(aq) → 2NacI_(aq) + CO_2(aq) + (x+1)H₂O_(I)

C_AV_A/C_BV_B     =  n_A/n_B

C_A = Molar concentration of HCI_(aq) in moldm³

V_A = Volume of acid used in cm³ = 24.80cm³

C_B = Molar concentration of Na₂Cu₃ xH₂O in moldm³

n_A = 2

n_B = 1

(b)(i) concentration of C in moldm^-3 = ? From the equation of reaction:

C_AV_A/C_BV_B     =  n_A/n_B

C_A = 0.200 moldm³     V_A = 24.80cm³

C_B = ?                          V_B = 25.00cm³

Substitution of known values

0.200 x 24.80/ C_B x 25.00 = 2/1

C_B = 1×0.200×24.80/2×25.00

C_B­ = 0.0992 moldm^-3

(ii) Concentration of C in g dm^-3 = ?

500cm² → 14.3 g

1000cm3 →14.3/500 x 1000² g

= 28.6 g dm^-3

(iii) Molar mass of Na₂CO₃ xH₂O

Molar conc in moldm^-3 = conc in g dm^-3 / molar mass

Therefore: Molar mass g mol^-1 = conc in g dm^-3 / molar conc in moldm^-3

= 28.6 g dm^-3/0.0992 moldm^-3

= 288.3065

Approximately 288 g mol^-1

(iv) Value of x in Na₂CO₃ xH₂O?

[H = 1.0, C = 12.0, O = 16.0, Na = 23.0]

Na₂CO₃ xH₂O = 288

2(23) + 12 + 3 (16) + x (2(I) + 16) = 288

46 + 12 + 48 + 18x  = 288

106 + 18x        = 288

18x      = 288

18x      = 182

x       = 182/18

x       = 10.11

x approximately 10

2	Test	Observation	Inference
(a)	F + distil water + stir + filter	Effervescence (bubbling) occurs, colourless and odourless gas evolved after filtration pale blue/colourless filtrate and green residue
(b)(i)	Filtrate + NaOH(aq) in drops then in excess	White precipitate formed   Precipitate insoluble in excess NaOH(aq)	Ca2+/Pb2+   Ca2+ present

(b)(ii)	Filtrate + NH3(aq) in drops then in excess	No visible reaction   No visible reaction OR	Ca2+ present   Ca2+ confirmed
(b)(i)	Filtrate + NaOH(aq) in drops then in excess	Blue gelatinous precipitate formed   Precipitate insoluble in excess	Cu2+  is present
(b)(ii)	Filtrate + NH3(aq) in drops then in excess	Pale (light) blue gelatinous precipitate formed   Precipitate dissolves to form a deep blue solution	Cu2+     Cu2+  is confirmed
(c)	Filtrate + NHO3(aq) + AgNO3(aq)	No visible reaction No gas involved White precipitate formed	CuI-  is present
(d)(i)	Residue + HNO3(aq)	Efferveness occurs, colourless and odourless gas evolves that turn blue litmus paper to red and turns lime water milky	CO2(g) CO32- present
(d)(ii)	Solution from 2(d)(i) + NaOH(aq) in drops then in excess	Blue precipitate formed   Precipitate insoluble in excess NaOH(aq)	Cu2+    Cu2+   present

3 (a)(i) Solution of lime juice turns to pink or red. (ii) The FeCI₃ solution changes colour from brown to green and a yellow deposit. (iii) The purple colour of the KMnO₄ solution turns colourless or decolourised. (iv) The solution of K₂CO₃ reacts with the addition of ethanoic acid to evolve a colourless, odourless gas with bubbling of effervescence.

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Tips on How to Pass NECO Examination 2023

If you want to Past the NECO Examination this year, you will need to follow the instructions below.

• Practice daily with NECO Past Questions and Answers
• Write out your subjects, the dates and time.
• Engage in general revision few days to the examination and dwell more on the subjects you find difficult.
• Focus on only your first paper a week to the exam. This would make it sweet and you will have energy to read for other papers.
• Don’t read any other subject when it is two days to a particular subject.
• When you have two papers that are separated by only one day, read the second one first before going to the subject you have first.
• Ensure to be in the NECO examination venue at least two hours to the examination so that you would be balanced.
• Try to be up to date in cases of changes in the timetable.
• Have a personal copy of the NECO timetable and syllabus.
• Go through your timetable daily so that you don’t miss any paper.
• Don’t go to the hall when you are not having paper that day.

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