Chemistry Test

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Chemistry Test - 16

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Weekly Quiz Competition

Question 1
1 / -0

The major role of fluorspar (CaF₂) which is added in small quantity in the electrolytic reduction of alumina dissolved in fused cryolite (Na₃AlF₆) is :
I. to act as a catalyst
II. to make the fused mixture very conduction
III. to lower the temperature of melting
IV. to decrease the rate of oxidation of carbon at the anode

A
I, II

B
II, III

C
I, II, III

D
III, IV

Solution

Fluorspar (CaF₂) is added in small quantity in the electrolytic reduction of alumina dissolved in fused cryolite (Na₃AlF₆). Addition of cryolite and fluorspar increases the electrical conductivity of alumina and lowers the fusion temperature to around 1140 K.
Question 2
1 / -0

Subatomic particle discovered by J. Chadwick was :

A
protons

B
neutrons

C
electrons

D
all of the above

Solution

J. Chadwick discovered subatomic particle named neutrons
Question 3
1 / -0

0.5 molal solution acetic acid (M.W. = 60) in benzene (M.W. = 78) boils at 80.80 °C. The normal boiling point of benzene is 80.10 °C and Δ_vap H = 30.775 KJ/mol. Which of the following option is correct regarding percent of association of acetic acid in benzene.

A
53.2

B
0.532

C
93.6

D
0.936

Solution
Question 4
1 / -0

Which of the following is/are example(s) of reversible reaction?

A
Formation of ammonia from nitrogen and hydrogen

B
Thermal decomposition of hydrogen chloride

C
Passage of nitrogen and oxygen through electric arc

D
All of the above

Solution

All the options are examples of reversible reaction.
Question 5
1 / -0

Calculate the number of atoms present in 71g of Cl₂.

A
1.205×10⁻²⁴ atoms

B
1.205×10²³atoms

C
1.205×10²⁴ atoms

D
1.205×10⁻²³ atoms

Solution

Weight of $C l_{2} = 71 g$
Molecular weight of $C l_{2} = 71 g / m o l$
Number of moles of $C l_{2}$
$= \frac{71 g}{71 g / g a t o m} = 1$ moles.
The Avogadro's number is 6.023 x 10²³ molecules/mol.
The number of atoms of Cl₂ = 2 atoms/molecule x1 mol x 6.023 x 10²³ molecules /mol
= 1.205 x 10²⁴ atoms
Question 6
1 / -0

Which one of the following ions is the most stable in aqueous solution?

(At. No. are: Ti = 22, V = 23, Cr = 24, Mn = 25)

A
Mn³⁺

B
Cr³⁺

C
V³⁺

D
Ti³⁺

Solution
Question 7
1 / -0

For the reaction between KMnO₄ and H₂O₂, the number of electrons transferred per mol of H₂O₂ is?

A
One

B
Two

C
Three

D
Four

Solution

The half reactions are
$2 M n O_{4}^{-}+16 H^{+}+10 e^{-} \rightarrow 2 M n^{+2}+8 H_{2}$
$5 H_{2} O_{2} \rightarrow 5 O_{2}+10 H^{+}+10 e^{+}$

The number of electron transferred per mole of hydrogen peroxide = 10/2 = 5 Hence, option B is the correct answer.
Question 8
1 / -0

Electronic configuration of only one P block element is exceptional. One molecule of that element consists of how many atoms of it?

A
One

B
Two

C
Three

D
Four

Solution

P-block element show general electronic configuration of ns²np1⁻⁶.
But, He is the only p-block element which shows the exceptional electronic configuration of 1s².
Since it is the noble gas, it is monoatomic.
Thus, one molecule of He contains only one atom.
Question 9
1 / -0

A gas X at 1 atm is bubbled through a solution containing a mixture of 1 M Y− and 1 M Z− at 25 C. If the reduction potential of Z > Y > X then _____________.

A
Y will oxidize X and not Z

B
Y will oxidize Z and not X

C
Y will oxidize both X and Z

D
Y will reduce both X and Z

Solution

Y will oxidize X and not Z
Question 10
1 / -0

Which one of the following statements is incorrect?

A
Greater is the nuclear charge,greater is the electron gain enthalpy

B
Nitrogen has almost zero electron gain enthalpy

C
Electron gain enthalpy decrease from fluorine to iodine in the group

D
Chlorine has highest electron gain enthalpy

Solution

Electron gain enthalpy is the energy released when an electron is added to an isolated gaseous atom. Its value is negative and the ease with which an atom accepts electrons its electron gain enthalpy becomes more negative (that is, its value increases).
With an increase in nuclear charge the electron gain enthalpy also increases.
Due to the extra stability of nitrogen (it has half filled valence shell [He]1s²2p³, which provides extra stability to it), it is very difficult to add electron to it. Therefore, it has almost zero electron gain enthalpy.
In general on moving down the group, the electron gain enthalpy decreases due to an increase in the atomic size, but on moving from F to Cl the electron gain enthalpy increases. Due to the very small size of F atom and absence of 3^rd shell, the incoming electron experiences repulsion due to the valence electrons and its electron gain enthalpy is less than Cl. After Cl the electron gain enthalpy follows the general order and decreases on moving down to Br and I.

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Chemistry Test - 16

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Chemistry Test - 16

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Question 1

I, II

II, III

I, II, III

III, IV

Solution

Question 2

protons

neutrons

electrons

all of the above

Solution

Question 3

53.2

0.532

93.6

0.936

Solution

Question 4

Formation of ammonia from nitrogen and hydrogen

Thermal decomposition of hydrogen chloride

Passage of nitrogen and oxygen through electric arc

All of the above

Solution

Question 5

1.205×10−24 atoms

1.205×1023 atoms

1.205×1024 atoms

1.205×10−23 atoms

Solution

Question 6

Mn3+

Cr3+

V3+

Ti3+

Solution

Question 7

One

Two

Three

Four

Solution

Question 8

One

Two

Three

Four

Solution

Question 9

Y will oxidize X and not Z

Y will oxidize Z and not X

Y will oxidize both X and Z

Y will reduce both X and Z

Solution

Question 10

Greater is the nuclear charge,greater is the electron gain enthalpy

Nitrogen has almost zero electron gain enthalpy

Electron gain enthalpy decrease from fluorine to iodine in the group

Chlorine has highest electron gain enthalpy

Solution

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1.205×10⁻²⁴ atoms

1.205×10²³atoms

1.205×10²⁴ atoms

1.205×10⁻²³ atoms

Mn³⁺

Cr³⁺

V³⁺

Ti³⁺