P-block Group 16 - Chalcogens(11th And 12th > Chemistry ) Questions and answers for exam Preparation

11th And 12th > Chemistry

P-BLOCK GROUP 16 - CHALCOGENS MCQs

Total Questions : 15 | Page 1 of 2 pages

Question 1.

Of the given hydrides of group 16 Elements, which is the most stable thermodynamically?

$H_{2} T e$
$H_{2} S$
$H_{2} O$
$H_{2} S e$

Discuss Question

Answer: Option C. ->

H_{2} O

:
C
As we go down the group, the electronegativity of the central atom decreases while the atomic size increases. This causes the

E - H

bond to weaken as we go down the group. Hence the thermal stability order is as

H_{2} O > H_{2} S > H_{2} S e > H_{2} T e > H_{2} P o

Question 2.

Finely divided metals and metal oxides on reaction with hydrogen peroxide liberate __ gas.

Discuss Question

Answer: Option C. ->

H_{2} O

:
Hydrogen peroxide readily breaks down in the presence of finely divided metals to liberate oxygen gas:

2 H_{2} O_{2} + M e t a l \to 2 H_{2} O (l) + O_{2} (g)

Question 3.

Compared to other group 16 elements, the anomalous behavior of Oxygen is due to:

Small atomic size
High electronegativity
Both (A) and (B)
None of these

Discuss Question

Answer: Option C. -> Both (A) and (B)
:
C
Among the Chalcogens, Oxygen shows considerable anomalies. For instance, Oxygen exists as a diatomic gas while the other chalcogens are all solids at room temperature and 1atm pressure. Further, oxygen forms strong and stable

p π - p π

double bonds (as in the case of

O_{2}

molecule) whereas the other elements tend not to. Also, the Oxygen - Oxygen single bond is weaker compared to the Element - Element single bonds of other chalcogens.
All this can be attributed to the small atomic size and high electro negativity of Oxygen.

Question 4.

Which of the following release oxygen on heating at high temperature?

$K_{2} C r_{2} O_{7}$
$K M n O_{4}$
$K C l O_{3}$
All of these

Discuss Question

Answer: Option D. -> All of these
:
D
Strongly heating Potassium dichromate, Potassium Permanganate or Potassium Chlorate gives oxygen gas.
Heating above

400^{\circ} C

, the following reactions takes place

4 K_{2} C r_{2} O_{7} \to 4 K_{2} C r_{2} O_{4} + 2 C r_{2} O_{3} + 3 O_{2}

2 K M n O_{4} \to K_{2} M n O_{4} + M n O_{2} + O_{2}

2 K C l O_{3} \to 2 K C l + 3 O_{2}

Thus all of them release oxygen gas on heating above

400^{\circ} C

. These reactions can be used in the preparation of oxygen gas in laboratory.

Question 5.

Electrolysis of water gives dioxygen gas - True or False?

True
False
$K C l O_{3}$
All of these

Discuss Question

Answer: Option A. -> True
:
A
In an electrolytic setup anode is the place where oxidation takes place and cathode is the place where reduction takes place.

O^{- 2}

looses two electrons at the anode to form oxygen, where as

H^{+}

gain electron at the cathode to form hydrogen gas.
Oxidation is nothing but loss of electrons and reduction is nothing but gain of electrons.
Electrolysis of water gives oxygen

(O_{2})

gas at anode and hydrogen

(H_{2})

gas at cathode and it can be separated and stored in cylinders

Question 6.

For which of the following process is Oxygen a prerequisite?

Inspiration
Expiration
Both (A) and (B)
Inspiration and combustion

Discuss Question

Answer: Option D. -> Inspiration and combustion
:
D
Oxygen is the major constituent during inspiration (inhalation) and combustion because both these processes cannot occur without oxygen. Oxygen from inspiration is used to combust the food to release energy and any fuel when combusted, releases energy. Hence oxygen is a must for combustion.

Question 7.

For patients who suffer from low oxygen levels, only "humidified oxygen" is supplied as opposed to dry oxygen gas - True or False?

True
False
Both (A) and (B)
Inspiration and combustion

Discuss Question

Answer: Option A. -> True
:
A
If the oxygen gas is not Humidified before entering patient’s body, it then causes drying of upper respiratory tract. Therefore, always humidified oxygen is used in hospitals to supply to the patients.

Question 8.

We humans have known elemental Sulphur from the earliest times. In the last two decades, the allotropy of sulfur has been explored in great detail. The most common naturally occurring allotrope, $S_{8}$ cyclo-octasulphur, has a puckered three dimensional “crown” like arrangement of atoms around the ring. This homocyclic allotrope forms “needle-like” crystals above $95^{\circ}$ C, but below that temperature, crystallizes in a “chunky” fashion. The crystals, which are referred to as monoclinic and rhombic forms, differ simply in the way in which the molecules pack. These are allotropes of each other – True or False?

True
False
Oxygen
Polonium

Discuss Question

Answer: Option B. -> False
:
B
The question looks long for a true or false type doesn’t it. Shall we keep the answer very short – yes?
Polymorphs are defined as different crystal forms in which identical units of the same compound are packed differently. Strictly speaking, the three varieties of cyclo-octasulphur – the

α

-Sulphur,

β

-Sulphur and the

γ

-Sulphur are all polymorphs and not allotropes. Allotropes contain different molecular units!
The repeating molecular unit of cyclo-octasulphur – the

S_{8}

molecule looks like:

We Humans Have Known Elemental Sulphur From The Earliest Tim...

Question 9.

Sulphur can also exist in an amorphous form – True or False?

True
False
Oxygen
Polonium

Discuss Question

Answer: Option A. -> True
:
A
When heated to

113^{\circ} C

Orthorhombic sulphur melts and if we continue heating this molten yellow liquid, it darkens above

160^{\circ} C

and becomes more viscous as the Sulphur rings break open and polymerize. The resulting helical

S_{n}

polymers can be extracted from the melt by pouring the molten Sulphur in water (called quenching). This super-cooled liquid is a metastable rubber-like material that slowly converts back to stable

α - S_{8}

at room temperature. Different polymeric chains can have different number of atoms and isolating a particular strain becomes difficult. Obviously these polymeric forms are amorphous

Question 10.

Which of the following Chalcogens shows the highest tendency for catenation?