UNN Chemistry 2010/2011 DAY 1 Past Questions

Practice each question, then open it to see the full details.

Question 1

Crystallization is a better method of separation than precipitation because

A.precipitation tends to bring other solutes out of solution
B.crystallization is applicable to all solids
C.precipitation always involves salting out
D.crystallization can only be done at high temperatures

Objective

Question 2

Which of the following is not a chemical change?

A.burning of magnesium
B.rusting of iron
C.action of water on potassium
D.dissolving powdered sulfur in carbon disulfide

Objective

Question 3

An important ore of iron contains 72.36% iron and 27.64% oxygen. Determine its empirical formula

A.FeO
B.Fe₂O₃
C.Fe₃O₄
D.Fe₂O₃

Objective

Question 4

Which of the following decreases when a given mass of gas is compressed to half its initial volume

A.average intermolecular distance
B.frequency of collision
C.number of molecules present
D.atomic radius of each particle

Objective

Question 5

The densities of two gases X and Y are 2.5gdm^-3 and 10.0gdm^-3 respectively. What is the rate of diffusion of X relative to Y?

A.1:2:5
B.2:5:1
C.1:2
D.2:1

Objective

Question 6

The properties of elements are periodic functions of their

A.atomic number
B.atomic radius
C.atomic volume
D.mass number

Objective

Question 7

Which of the following solutions containing only hydroxyl ions will liberate hydrogen gas when reacted with Mg metals?

A.1.0 x 10^-5 moldm^-3
B.1.0 x 10^-13 moldm^-3
C.1.0 x 10^-3 moldm^-3
D.1.0 x 10^-2 moldm^-3

Objective

Question 8

In the redox reaction
2Fe²⁺ + Cl₂ ----> 2Fe³⁺ + 2Cl^-

A.Cl₂ is reduced because it has electrons
B.Cl₂ is reduced because its oxidation number has decreased
C.Fe²⁺ is reduced because it has lost electrons
D.Fe³⁺ is reduced because it has gained electrons

Objective

Question 9

During electrolysis of molten sodium chloride,

A.chlorine atom gains an electron
B.chloride ion gains an electron
C.chloride ion is oxidized
D.sodium ion is oxidized

Objective

Question 10

Coffee stains are removed with

A.turpentine
B.ammonia
C.borax in water
D.kerosene

Objective

Question 11

What is the value of ∆H for this reaction?
Fe₂O_3(s) + 3H₂O_(l) ----> 2Fe(OH)_3(s)

Substance	ΔH (KJ/mol)
Fe₂O_3(s)	-824.2
Fe(OH)_3(s)	-823.0
H₂O_(l)	-285.8

A.35.6 KJ
B.286.0 KJ
C.858.6 KJ
D.-536 KJ

Objective

Question 12

N_2(g)O ↔ 2NO_2(g)
∆H = +ve
What happens to the equilibrium constant of the reaction above if the pressure is increased?

A.it becomes zero
B.it decreases
C.it increases
D.it is unaffected

Objective

Question 13

Radioisotopes are used for the following EXCEPT

A.development of photographic films
B.generation of electricity
C.radio carbon dating
D.tracers in chemical reactions

Objective

Question 14

The common characteristics shared by iron and aluminium is that both

A.are extracted by reduction method
B.form only basic oxides
C.show oxidation states of +2 and +3
D.form soluble hydroxides

Objective

Question 15

In the reaction H₂C-=CH + 2HBr ---> X, X is

A.CH₃CBr₂CH₃
B.CH₃CH₂CHBr₂
C.CH₃CHBrCHBr
D.CH₂BrCH₂CH₂Br

Objective