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Chemistry Past Questions

Study and practice Chemistry past questions with answers and detailed explanations. Then test your knowledge using our interactive CBT practice platform and prepare confidently for your upcoming examinations.

81 questions JAMB 2505 WAEC 1623 NECO 168 CUSTOM 10

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81 questions

Question 1 of 20 81 total questions

Question 31

jamb 1990

The label on a reagent bottle containing a clear organic liquid dropped off.The liquid was neutral to litmus and gave a colourless gas with metallic sodium. The liquid must be an?

Aalkanoate

Balkaene

Calkanol

Dalkane

View Explanation & Discuss

Question 32

jamb 1990

A cycloalkane with the molecular formula C5H10 has ?

Aone isomer

Btwo isomers

Cthree isomers

Dfour isomers

View Explanation & Discuss

Question 33

jamb 1990

Which of the following compounds gives a yellow residue when heated and also reacts with aqueous sodium hydroxide to give a white gelatinous precipitate soluble in excess sodium hydroxide solution?

A(NH₄)CO₃

BZnCO₃

CAl₂(SO₄)₃

DPbCO3

View Explanation & Discuss

Question 34

jamb 1990

To make coloured glasses, small quantities of oxides of metals which form coloured silicates are often added to the reaction mixture consisting of Na₂CO₃ and SiO₂. Such a metals is a?.

Apottasium

Bbarium

Czinc

Dcopper

View Explanation & Discuss

Question 35

jamb 1990

Sodium hydroxide should be stored in properly closed containers because it?

Areadily asborbs water vapour to air

Bis easily oxidize by atmospheric oxygen

Cturns golden yellow when exposed to light

Dmelts at a low temperature

View Explanation & Discuss

Question 36

jamb 1990

The major component of the slag from the production of iron is?

Aan alloy of calcium and iron

Bcoke

Cimpure iron

Dcalcium trioxosilicate (IV)

View Explanation & Discuss

Question 37

jamb 1990

Coal fire should not be used in poorly ventilated rooms because ?

Aof the accumulation of CO₂ which causes dep sleep

Bit is usually too hot

Cof the acumulation of CO which causes suffocation

Dit removes most most of the gases in the rooms

View Explanation & Discuss

Question 38

jamb 1990

Which of the following metals will liberate hydrogen from steam or dilute acid?

ACopper

BIron

CLead

DMercury

View Explanation & Discuss

Question 39

jamb 1990

A metallic oxide which reacts with both HCl and NaOH to give salt and water only can be classified as?

Aan acidic oxide

Ba basic oxide

Ca neutral oxide

Dan amphoteric oxide

View Explanation & Discuss

Question 40

jamb 1990

In the Haber process for the manufacture of ammonia, the catalyst commonly used is finely divided ?

Avanadium

Bplatinum

Ciron

Dcopper

View Explanation & Discuss

Question 41

jamb 1990

Which of the following tests will completely identify anyone of surphur (VI) oxide, hydrogen, carbon (IV) oxide and nitrogen (II) oxide?

APass each gas into water and test with blue litmus paper

BPass each gas into lime water

CExpose each gas to atmospheric air

DPass each gas to concentrated tetraoxosulphate (IV) acid

View Explanation & Discuss

Question 42

jamb 1990

The brown fumes given off when trioxonitrate (V) acid is heated consist of ?

ANO₂ and O₂

BH₂O and NO₂

CNO_2' O₂ and H₂O

DNO, NO₂ and H₂O

View Explanation & Discuss

Question 43

jamb 1990

Which of the following gases can be collected by the upward displacement of air?

ANO

BH ₂

CNH₃

DCl ₂

View Explanation & Discuss

Question 44

jamb 1990

In the reaction:
2Hl_(g) ↔ H_2(g) + l_2(g)' ΔH = 10 kj;

The concentration of iodine in the equilibrium mixture can be increased by?

Araising the pressure

Braising the temperature

Cadding a catalyst

Dlowering the pressure

View Explanation & Discuss

Question 45

jamb 1990

Which of the following samples will react fastest with dilute trioxonitrate (V) acid?

A5 g of lumps of CacO₃ at 25°C

B5 g of powered CacO₃ at 25°

C5 g of lumps of CaCO₃ at 50°C

D5 g of powered CaCO₃ AT 50°C

View Explanation & Discuss

Question 46

jamb 1990

Iron galvanized with zinc is cathodically protected from corrosion. This is because?

Azinc has a more positive oxidation potential than iron

Bzinc has less positive oxidation potential than iron

Cbith have the same oxidation potential

Dzinc is harder than iron

View Explanation & Discuss

Question 47

jamb 1990

Fe\(_2\)O\(_{3(s)}\) + 2Al\(_{(s)}\) → Al\(_2\)O\(_3\) + 2Fe\(_{(s)}\). If the heats of formation of Al\(_2\)O\(_3\) and Fe\(_2\)O\(_3\) are - 1670 kJmol\(^{-1}\) and - 822 kJmol\(^{-1}\) respectively, the enthalpy change in kJ for the reaction is ?

A+2492

B+848

C-848

D-2492

View Explanation & Discuss

Question 48

jamb 1990

In the reaction 1O^-₃ + 5l^- + 6H⁺ → 31₂ + 3H₂O, the oxidizing agent is?

AH⁺

Bl^-

C1O^-

Dl₂

View Explanation & Discuss

Question 49

jamb 1990

Cr\(_2\)O\(_7\)\(^{2-}\) + 6Fe\(^{2+}\) + 14H\(^+\) → 2Cr\(^{3+}\) +6Fe\(^{3+}\) + 7H\(_2\)O. In the above , the oxidation number of chromium changed from?

A+7 to +3

B+6 to +3

C+5 to +3

D-2 to +3

View Explanation & Discuss

Question 50

jamb 1990

In a reaction: \(SnO_{2} + 2C → Sn + 2CO\) the mass of coke containing 80% carbon required to reduce 0.302 kg of pure tin oxide is?
(Sn - 119, O - 16, C - 12).

A0.40 kg

B0.20 kg

C0.06 kg

D0.04 kg

View Explanation & Discuss

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