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Chemistry Past Questions

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2,505 questions JAMB 2505 WAEC 1623 NECO 168 CUSTOM 10

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2,505 questions

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Question 271

jamb 2018

In the upper atmosphere, the ultra-violet light breaks off a free chlorine atom from chlorofluorocarbon molecule. The effect of this is that the free chlorine atom will

Abe very reactive and will attack ozone

Bbe non-reactive and will not attack ozone

Cnot change the level of ozone in the atmosphere

Dincrease the level of ozone in the atmosphere

View Explanation & Discuss

Question 272

jamb 2018

Which of the following separation techniques can be employed in obtaining solvent from its solution?

AEvaporation

BDistillation

CFiltration

DPrecipitation

View Explanation & Discuss

Question 273

jamb 2018

A sample of hard water contains some calcium sulphate and calcium hydrogen carbonate. The total hardness may therefore be removed by

Aboiling the water

Badding excess calcium hydroxide

Cadding a calculated amount of calcium hydroxide

Dadding sodium carbonate

View Explanation & Discuss

Question 274

jamb 2018

In the removal of water hardness, permutit is regenerated with a strong solution of

ANaOH

BNa\(_3\)SO\(_4\)

CNa\(_3\)CO\(_3\)

DNaCl

View Explanation & Discuss

Question 275

jamb 2018

When large hydrocarbon molecules are heated at high temperature in the presence of a catalyst to give smaller molecules, the process is known as

Adisintegration

Bpolymerization

Ccracking

Ddegradation

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Question 276

jamb 2018

Which of the compounds is composed of Al, Si, O and H?

AEpson salt

BLimestone

CClay

DUrea

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Question 277

jamb 2018

H\(_2\) S\(_{(g)}\) + Cl\(_{2(g)}\) → 2HCl\(_{(g)}\) + S\(_{(g)}\) In the reaction above, the substance that is reduced is

AH\(_2\)S

CHCl

DCl\(_2\)

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Question 278

jamb 2018

The elements in the periodic table are listed in order of increasing

Arelative atomic number

Batomic mass

Crelative isotopic mass

Dnuclear charge

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Question 279

jamb 2018

The alkanoic acid found in human sweat is

ACH\(_3\)-COOH

BCH\(_3\)—CH\(_2\)—COOH

CH-COOH

DCH\(_3\)

View Explanation & Discuss

Question 280

jamb 2018

The general formula of alkanones is

ARCHO

BR\(_2\)CO

CRCOOH

DRCOOR

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Question 281

jamb 2018

The situation obtained when a perfect gas expands into a vacuum is

AΔH is positive and TΔ S is zero

BΔH is positive and T Δ S is negative

CΔH is negative and TΔ S is zero

DΔH is zero and T Δ S is positive

View Explanation & Discuss

Question 282

jamb 2018

3H\(_{2(g)}\)+ N\(_{2(g)}\)⇔ 2NH\(_{3(g)}\) ; H= -ve
In the reaction above, lowering of temperature will

Ahave no effect on the equilibrium position

Bincrease the rate of both the forward and reverse reactions equally

Cfavour the forward reaction

Dfavour the reverse reaction

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Question 283

jamb 2018

Sieving is a technique used to separate mixtures containing solid particles of

Asmall sizes

Blarge sizes

Cdifferent sizes

Dthe same size

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Question 284

jamb 2018

If the molecular mass of tetraoxosulphate (VI) acid is 98, calculate its vapour density.

A196

B49

C106

D82

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Question 285

jamb 2018

Which of these alloys contains copper?

Asolder

Bsteel

Cpermallory

Dbronze

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Question 286

jamb 2018

Calculate the percentage composition of oxygen in calcium trioxocarbonate(IV) [Ca=40, C=12, O=16]

A16

B48

C40

D12

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Question 287

jamb 2018

The ionic radii of metals are usually

Agreater than their atomic radii

Bunaffected by the charge on the ion

Cthe same as their atomic radii

Dless than their atomic radii

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Question 288

jamb 2018

In electrovalency, the oxidation number of the participating metal is always

Adecreasing

Bincreasing

Cconstant

Dneutral

View Explanation & Discuss

Question 289

jamb 2018

The derivative of benzene that can be used in making explosives is

Aaniline

Bxylene

Cphenol

Dtoluene

View Explanation & Discuss

Question 290

jamb 2018

During the electrolysis of copper II sulphate between platinum electrodes, if litmus solution is added to the anode compartment

Athe litmus turns blue but no gas is evolved

Bthe litmus turns blue and oxygen is evolved

Cthe litmus turns blue and hydrogen is evolved

Dthe litmus turns red and oxygen is evolved

View Explanation & Discuss

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