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Chemistry Past Questions

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49 questions JAMB 2505 WAEC 1623 NECO 168 CUSTOM 10

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Past Questions

49 questions

Question 1 of 9 49 total questions

Question 21

jamb 1990

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

ANO

BH ₂

CNH₃

DCl ₂

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Question 22

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

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Question 23

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

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Question 24

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

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Question 25

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

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Question 26

jamb 1990

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

AH⁺

Bl^-

C1O^-

Dl₂

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Question 27

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

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Question 28

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

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Question 29

jamb 1990

Which of the following is a physical change?

AThe bubbling of chlorine into water

BThe bubbling of chlorine into a jar contanining hydrogen

CThe dissolution of sodium chloride in water

DThe passing of steam over heated iron

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