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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 20 49 total questions

Question 11

jamb 1979

The reaction between hydrogen and iodine may be represented by the equation H₂(g)+ I₂(g) → 2HI(g), and is exothermic. Therefore

Aan increase in temperature favours the forword reaction

Ban increase in pressure favours the backward reaction

Cboth pressure and temperature muct be increased to favour the forward reaction

Da decrease in temperature will favour the forward reaction

Ea decrease in pressure and an increase in temperature will favour the forward reaction

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Question 12

jamb 1979

Starch can be converted to ethyl alcohol by

Adistillation

Bfermentation

Cisomerization

Dcracking

Ecooking

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Question 13

jamb 1979

Calcium hydroxide and ammonium chloride when heated together will give an important product. This compound may be obtained dry by

Adissolving it in water, recrystallizing it and then drying in the oven

Bpassing it through a concentrated aqueous solution of sodium hydroxide

Cpassing it through calcium oxide

Dpassing it through concentrated sulphuric acid

Epassing it through anhydrous calcium choride

View Explanation & Discuss

Question 14

jamb 1979

In which of the following reactions is sulphur dioxide acting as an oxidizing agent?

ASO ₂ + 2HNO₃ →H₂SO₄ + NO₂ + Heat

B2SO₂ + 2H₂O + O₂→ 2H₂SO₄

CSO₂ + 2H₂O + CI₂→ H₂SO₄ + 2HCI

DSO₂ + 2H₂S → 3S + 2H₂O

ESO₂ + H₂O → H₂SO₃

View Explanation & Discuss

Question 15

jamb 1979

An anhydride is?

Aa compound wich has no water of crystallization

Ban oxide whose solution in water has a PH greater than 7

Can oxide whose solution in water has a PH less than 7

Dan oxide that has hydrogen atoms

Ean amphoteric oxide

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Question 16

jamb 1979

In the redox reaction\( 2Fe^{2+} + CI_2 → 2Fe^{3+} + 2Cl^-\)

ACl₂ is reduced because it has lost electrons

BCl₂ is reduced because its oxidation number has decreased

CCl₂ is reduced because its molecule is change to two ions

DFe²⁺ is reduced because it has lost electrons

EFe²⁺ is reduced because it has gained electrons

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Question 17

jamb 1979

In the extraction of aluminum from purified bauxite by electrolysis, cryolite is used because

Ait makes bauxite a better conductor of electricity

Bit makes bauxite melt at a lower temperature

Cit makes aluminium purer

Dit prevents aluminium from getting oxidized

Eit protects the carbon electrodes used in the process

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Question 18

jamb 1979

Which one of these compounds will NOT give an oxygen gas on heating?

AManganese dioxide

BHydrogen peroxide

CZinc nitrate

DSodium nitrate

EAmmonium nitrate

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Question 19

jamb 1979

0.1 Faraday of electricity was passed through a solution of copper (ll) sulphate. The maximum weight of copper deposited on the cathode would be [Cu = 64]

A64.0g

B32.0g

C16.0g

D6.4 g

E3.2g

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Question 20

jamb 1979

Indicate which of the following statements is not true as we move from left to right along the periodic Table:

Aatomic number of elements increases

Batomic mass of elements increases

Celectropositive character of elements increases

Delectronegative character of elements increases

Enumber of electrons in the outermost orbits of element increases

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Question 21

jamb 1979

When a piece of charcoal enclosed in a cylinder containing air is ignited

Athe toatl volume of air is increased

Bthe relative amount of oxygen present is increased

Cthe relative amount of nitrogen present is decreased

Dthe relative amount of carbondioxide present is increased

Ethe ratio of oxygen to nitrogen in the system is increased

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Question 22

jamb 1979

The empirical formula of an oxide of nitrogen containing 30.4 per cent of nitrogen is (N=14.0,O=16.0)

AN₂O₂

BNO

CNO₂

DN₂O

EN₂O₃

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Question 23

jamb 1979

In the electrolysis of dilute sulphuric acid using platinum electrodes, the products obtained at the anode and cathode are:
Anode Cathode

ASulphur hydrogen

BHydrogen oxygen

COxygen Hydrogen

DHydrogen sulphate ions

ESulphur oxygen

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Question 24

jamb 1979

12 g of solid protassium chlorate (KCIO) were added to 40 g of water and heated to dissolve all the solid. As the solution cools, crystals of potassium chlorate at 66 oC. The solubility of potassium chlorate at 66 oC is therefore?

A66

B33

C10

D20

E30

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Question 25

jamb 1979

If chlorine gas is bubbled into water and then this yellowish-green coloured solution is exposed to bright sunlight for a while

Athe solution will give out chlorine gas and hydrogen chloride gas

Bthe solution will produce chlorine gas and oxygen

Cthe solution will give out solution will producing hypochloric acid

Dthe solution is decomposed giving out oxygen, hydrogen and chlorine

Ethe solution will give out oxygen gas leaving behind aqueous hydrochloric acid

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Question 26

jamb 1979

When ammonium, potassium and calcium carbonates are each separately heated

Anone of them will decompose

Beach of them will decompose to give carbondioxide and the respective oxide

Cammonium carbonate and potassium carbonate will not decompose

Donly ammonium carbonate and the respective oxide

Eammonium carbonate will decompose to give carbondioxide, water and ammonia

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Question 27

jamb 1979

How many grams of HBr would exactly be required to react with 2 g of propyne? (C =12, H=1, Br = 80)

A4. 1 g

B6. 1 g

C8. 1g

D16.2g

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Question 28

jamb 1979

\(50cm^{3}\) of hydrogen are sparked with \(20cm^{3}\) of oxygen at \(100°C\) and \(1atm\) . The total volume of the residual gases in

A50 cm³

B10 cm³

C40 cm³

D30 cm³

E70 cm³

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Question 29

jamb 1979

Helium atoms are chemically unreactive because

Athere are no electrons around the nucleus

Bthe number of protons equals the number of electrons

Cthere are equal number of protons and neutrons in the nucleus

Dthe outer electron shell is completely filled

Ethe atoms contain only protons

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Question 30

jamb 1979

Which of the following contains two amphoteric oxides?

Asodium oxide, Zinc oxide , Magnesium oxide

BAluminium oxide, Calcium oxide, Zinc oxide

CPotassium oxide, Lithium oxide, Carbon monoxide

DSilver oxide, Lead oxide, Sodium oxide

ESulphur dioxide, Aluminium oxide, Carbon monoxide

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