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Chemistry Past Questions

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123 questions JAMB 2505 WAEC 1623 NECO 168 CUSTOM 10

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Past Questions

123 questions

Question 1 of 20 123 total questions

Question 1

neco 2003

What is the number of moles of Na\(_H\)CO\(_3\) in 250cm\(^3\) of its solution if the solution contains 8.4 g of Na\(_H\)CO\(_3\) in 1 dm\(^3\) of the solution. [Na = 23, 0 = 16, C = 12, H = 1)

B0.25

C0.05

D0.025

E0.01

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Question 2

neco 2003

In the reaction 2H₂S(g) + SO₂(g) → 2H₂SO(I)+3S(s)SO₂is acting as _agent

Aa bleaching

Ba dehydrating

Can oxidizing

Da precipitating

Ea reducing

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Question 3

neco 2003

What is the change in the oxidation number of phosphorus in the following reaction?

4P(s) + 5O₂(ag) → 2P₂O₅(s)

A0 to 2

B0 to 5

C4 to 2

D4 to 5

E4 to 10

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Question 4

neco 2003

Chlorine displaces bromine from aqueous potassium bromide because

Abromine is a liquid at room temperature

Bbromine is weakly acidic.

Cbromine has a greater atomic radius than chlorine

Dchlorine is a stronger oxidising agent than bromine.

Ethe density of chlorine is less than the density of bromine.

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Question 5

neco 2003

The pH of water is 7.

What is the pH of orange juice?

Babove 10

Cbelow 2

Dbetween 5.5 and 6.5

Ebetween 7.5 and 8.5

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Question 6

neco 2003

Small amounts of compounds of transition metals are sometimes added to glass during manufacture in order to make the glass

Aacquire certain colours

Beasier to melt

Ceasier to mould

Dlittle brittle

Emore transparent

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Question 7

neco 2003

Which separation technique is routinely applied in the petroleum industry?

Achromatography

Bdistillation

Cevaporation

Dfractional crystallization

Efractional distillation

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Question 8

neco 2003

Which metal is extracted from bauxite?

Aaluminium

Bcalcium

Ccopper

Dmagnesium

Etin

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Question 9

neco 2003

Why is tetraoxosulphate(VI) acid NOT used for making carbon dioxide from calcium carbonate? It is

Aa dehydrating agent

Ba strong acid

Can oxidising agent

Ddibasic

Eforms insoluble calcium tetraoxosulphate(Vl)

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Question 10

neco 2003

Which hydrocarbon does NOT exhibit structural isomerism?

AC₃H₆

BC₄H₆

CC₄H₈

DC₄H₁₀

EC₅H₁₂

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Question 11

neco 2003

What is formed when starch is completely hydrolysed?

Afructose

Bglucose

Clactose

Dmaltose

Esucrose

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Question 12

neco 2003

Ethene decolourises acidified potassium tetraoxomanganate(VII) solution. Which gas will decolourise bromine water?

ACH₄

BC₂H₆

CC₃H₆

DC₃H₈

EC₆H₆

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Question 13

neco 2003

Which method is used for the purification of copper from its ore?

Adistillation

Belectrochemical

Celectrolysis

Dneutralization

Ereduction

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Question 14

neco 2003

What is the concentration (mol dm\(^{-3}\)) of a solution containing 28 g of potassium hydroxide per 100 cm\(^3\) of solution? (K=39; H=1; O=16)

A0.01

B0.05

C1.0

D5.0

E2.8

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Question 15

neco 2003

At s.t.p, a mole of chlorine occupies 22.4dm3. If the temperature is changed to 35°C and the pressure to 750mHg the of the new volume will be [Cl = 35.5]

A\(\frac{760\times 22.4\times 308}{750\times 273\times 35.5} dm^3 \)

B\(\frac{760\times 22.4\times 308}{750\times 273}dm^3 \)

C\(\frac{750\times 22.4\times 35.5}{760\times 273}dm^3\)

D\(\frac{760\times 22.4\times 35.5}{750\times 22.3\times 273}dm^3 \)

E\(\frac{760\times 22.4\times 35.5}{750\times 308}dm^3 \)

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Question 16

neco 2003

How many Faradays of electricity are required to liberate 9g of aluminium? [Al = 27]

A0.1

B0.3

D2.7

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Question 17

neco 2003

Which metal bromide is widely used in photography?

Acalcium bromide

Bmagnesium bromide

Cpotassium bromide

Dsilver bromide

Esodium bromide

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Question 18

neco 2003

What change will occur during the electrolysis of brine using carbon electrodes?

AChlorine will be given off at the anode

BOxygen gas will be given off at the anode

CSodium will be deposited at the cathode

DThe resulting solution, after electrolysis, will be acidic.

EThe volumes of hydrogen and chlorine given off during the same time are equal

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Question 19

neco 2003

Which metal is a constituent of both bronze and solder?

Acopper

Blead

Csilver

Dtin

Ezinc

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Question 20

neco 2003

An atom of element X has an electronic configuration of \( 1s^22S^22p^63s^23p^3. \) In which group of the periodic table is X?

A\( \text{0} \)

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