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All questions of p-Block Elements for NEET Exam

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Which of the following is a polar molecule ? [NEET 2013]
  • a)
    SF4
  • b)
    SiF4
  • c)
    XeF4
  • d)
    BF3
Correct answer is option 'A'. Can you explain this answer?

Rajesh Datta answered
SF4 has 4 bond pairs and 1 lone pair of electrons, sp3d hybridisation leads to irregular shapeand resultant
μ ≠ 0.

Among the following which is the strongest oxidising agent? [2009]
  • a)
    Br2
  • b)
    I2
  • c)
    Cl2
  • d)
    F2
Correct answer is option 'D'. Can you explain this answer?

Rajesh Datta answered
Standard reduction potential of halogens are positive and decreases from fluorine to iodine. Therefore halogens act as strong oxidising agent and their oxidising power decreases from fluorine to iodine.

Which of the following is the most basic oxide?
  • a)
    Sb2O3
  • b)
    Bi2O3 [2006]
  • c)
    SeO2
  • d)
    Al2O3
Correct answer is option 'B'. Can you explain this answer?

Nilotpal Gupta answered
More the oxidation state of the central atom (metal) more is its acidity. Hence SeO2 (O. S. of Se = +4) is acidic. Further for a given O.S., the basic character of the oxides increases with the increasing size of the central atom.
Thus Al2O3 and Sb2O3 are amphoteric and Bi2O3 is basic.

Which one of the following arrangements does not truly represent the property indicated against it?[2000]
  • a)
    Br2 < Cl2 < F2 : Electronegativity
  • b)
    Br2 < F2 < Cl2 : Electron affinity
  • c)
    Br2 < Cl2 < F2 : Bond energy
  • d)
    Br2 < Cl2 < F2 : Oxidising power
Correct answer is option 'C'. Can you explain this answer?

Krish Khanna answered
The bond energy of F2 < Cl2 due to more repulsion in between non-bonding electrons (2p) of F2 in comparision to non- bonding pair (3p) repulsion in Cl2, the bond energy of F2 < Cl2.
Bond energy (kJ mol–1) :

The formula for calcium chlorite is [1994]
  • a)
    Ca(ClO4)2
  • b)
    Ca(ClO3)2
  • c)
    CaClO2
  • d)
    Ca(ClO2)2
Correct answer is option 'D'. Can you explain this answer?

Shraddha Choudhury answered
The formula for calcium chlorite is Ca(ClO2)2. Let's break down the components of this compound to understand why this is the correct formula.

Calcium:
- Calcium is a metal with a +2 charge. It is represented by the symbol Ca in the periodic table.

Chlorite:
- Chlorite is a polyatomic ion with the formula ClO2-. It consists of one chlorine atom (Cl) bonded to two oxygen atoms (O), and it carries a -1 charge.

Formation of calcium chlorite:
- When calcium reacts with chlorite, the calcium ion (Ca2+) combines with two chlorite ions (ClO2-) to form calcium chlorite (Ca(ClO2)2).
- The calcium ion has a +2 charge, while each chlorite ion has a -1 charge. To balance the charges, two chlorite ions are needed for every calcium ion.

Explanation of options:

a) Ca(ClO4)2:
- This formula represents calcium perchlorate, not calcium chlorite. Perchlorate is a different polyatomic ion that consists of one chlorine atom and four oxygen atoms.

b) Ca(ClO3)2:
- This formula represents calcium chlorate, not calcium chlorite. Chlorate is another polyatomic ion that consists of one chlorine atom and three oxygen atoms.

c) CaClO2:
- This formula represents calcium hypochlorite, not calcium chlorite. Hypochlorite is a different polyatomic ion that consists of one chlorine atom and two oxygen atoms.

d) Ca(ClO2)2:
- This formula represents calcium chlorite, which is the correct compound. It consists of one calcium ion (Ca2+) bonded to two chlorite ions (ClO2-).

In summary, the correct formula for calcium chlorite is Ca(ClO2)2, as it consists of one calcium ion bonded to two chlorite ions.

Noble gases do not react with other elements because [1994]
  • a)
    They are mono atomic
  • b)
    They are found in abundance
  • c)
    The size of their atoms is very small
  • d)
    They are completely paired up and stable electron shells
Correct answer is option 'D'. Can you explain this answer?

Arnab Chavan answered
Why noble gases do not react with other elements?

Noble gases, also known as inert gases, are a group of elements that include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). These gases are characterized by their extremely low reactivity, which is due to their stable electron configurations. The correct answer to the question is option 'D', which states that noble gases do not react with other elements because they have completely paired up and stable electron shells.

Explanation:

1. Noble gases have completely paired up electron shells:
- Noble gases have full valence electron shells, meaning that their outermost energy level is completely filled with electrons.
- For example, helium has two electrons in its outermost energy level, neon has eight, and so on.
- This complete electron configuration gives noble gases a high degree of stability and a lack of reactivity.

2. Stable electron configuration:
- The stability of noble gases arises from the fact that their electron configurations follow the octet rule.
- The octet rule states that atoms tend to gain, lose, or share electrons to achieve a complete outer shell with eight electrons (except for helium, which only requires two electrons).
- Noble gases already have this stable electron configuration, so they have no need to gain, lose, or share electrons with other elements.

3. Lack of unpaired electrons:
- In chemical reactions, elements typically react to achieve a stable electron configuration.
- Most elements achieve this stability by gaining, losing, or sharing electrons to fill their outer energy levels.
- Noble gases, however, already have their outer energy levels fully filled with electrons, so they do not require any additional electrons.
- This lack of unpaired electrons makes noble gases unreactive and unlikely to form chemical bonds with other elements.

Conclusion:

In summary, noble gases do not react with other elements because they have completely paired up and stable electron shells. Their full outer energy levels provide a high degree of stability, making them unreactive and giving them the name "inert gases." This lack of reactivity is a result of their already fulfilled electron configurations, which do not require any additional electrons to achieve stability.

Which one of the following  arrangements does not give the correct picture of the trends indicated against it ? [2008]
  • a)
    F2 > Cl2 > Br2 > I2 : Oxidizing power
  • b)
    F2 > Cl2 > Br2 > I2 : Electron gain enthalpy
  • c)
    F2 > Cl2 > Br2 > I2 : Bond dissociation energy
  • d)
    F2 > Cl2 > Br2 > I2 : Electronegativity.
Correct answer is option 'B,C'. Can you explain this answer?

Nisha Pillai answered
From the given options we find option (a) is correct. The oxidising power of halogens follow the order F2 > Cl2 > Br2 > I2 . Option (b) is incorrect because it in not the correct order of electron gain enthalpy of halogens. The correct order is Cl2 > F2 > Br2 > I2 . The low value of F2 than Cl2 is due to its small size. Option (c) is incorrect. The correct order of bond dissociation energies of halogens is Cl2 > Br2 > F2 > I2 . Option (d) is correct. It is the correct order of electronegativity values of halogens. Thus option (b) and (c) are incorrect.

Which of the following oxy-acids has the maximum number of hydrogens directly attached to phosphorus? [1999]
  • a)
    H4P2O7
  • b)
    H3PO2
  • c)
    H3PO3
  • d)
    H3PO4
Correct answer is option 'B'. Can you explain this answer?

Smrity answered
In option a )no hydrogen attached directly to p
in option b) two H directly attached to P
in option c) one H directly attached to P
and in option d) no any hydrogen directly attached to P

so correct option is b

Polyanion formation is maximum in [1994]
  • a)
    Nitrogen
  • b)
    Oxygen
  • c)
    Sulphur
  • d)
    Boron
Correct answer is option 'C'. Can you explain this answer?

Harshitha Dey answered
Due to greater tendency for catenation, sulphur shows property of polyanion formation to a greater extent. For example, in polysulphides such as 

The acid which has a peroxy linkage is [1994]
  • a)
    Sulphurous acid
  • b)
    Pyrosulphuric acid
  • c)
    Dithionic acid
  • d)
    Caro’s acid
Correct answer is option 'D'. Can you explain this answer?

Vaibhav Basu answered
Caro’s acid is H2SO5 which contains one S – O – O – H peroxy linkage. It is also known as permonosulphuric acids.

Which of the following statements is false ? [1994]
  • a)
    Radon is obtained from the decay of radium
  • b)
    Helium is inert gas
  • c)
    Xenon is the most reactive among the rare gases
  • d)
    The most abundant rare gas found in the atmosphere is helium
Correct answer is option 'D'. Can you explain this answer?

Abhijeet Menon answered
False Statement:
The most abundant rare gas found in the atmosphere is helium. (Option D)

Explanation:
To determine the false statement among the given options, let's analyze each statement one by one:

a) Radon is obtained from the decay of radium:
This statement is true. Radon is a radioactive gas that is formed as a result of the decay of radium. Radium undergoes a series of radioactive decays, ultimately leading to the formation of radon.

b) Helium is inert gas:
This statement is true. Helium is classified as an inert gas because it has a stable electronic configuration with a complete outermost energy level. It does not readily react with other elements, making it chemically inert.

c) Xenon is the most reactive among the rare gases:
This statement is false. Xenon is actually the least reactive among the rare gases. Rare gases, also known as noble gases, are characterized by their low reactivity due to their stable electronic configurations. Xenon is particularly known for its low reactivity and is often used in lighting applications.

d) The most abundant rare gas found in the atmosphere is helium:
This statement is false. The most abundant rare gas found in the atmosphere is actually argon, not helium. Argon makes up about 0.93% of the Earth's atmosphere, making it the most abundant rare gas. Helium, on the other hand, is present in much smaller quantities and is only about 0.00052% of the atmosphere.

Therefore, the false statement is option D: The most abundant rare gas found in the atmosphere is helium.

Which of the following statements is not true ? [2003]
  • a)
    HF is a stronger acid than HCl
  • b)
    Among halide ions, iodide is the most powerful reducing agent
  • c)
    Fluorine is the only halogen that does not show a variable oxidation state
  • d)
    HOCl is a stronger acid than HOBr
Correct answer is option 'A'. Can you explain this answer?

Sanjana Bajaj answered
The correct answer is option A: HF is a stronger acid than HCl.

Explanation:
- In order to determine the strength of an acid, we need to compare their acidic properties, which can be measured by their ability to donate a proton (H+ ion) in a solution.
- The strength of an acid is determined by the stability of its conjugate base. A stronger acid will have a more stable conjugate base.
- In the given options, option A states that HF is a stronger acid than HCl. However, this statement is not true.
- HF is a weak acid, whereas HCl is a strong acid.
- The strength of an acid is based on the acidity constant (Ka). The higher the Ka value, the stronger the acid.
- For HF, the Ka value is relatively small (around 7 x 10^-4), indicating that it is a weak acid.
- On the other hand, HCl has a much larger Ka value (around 1 x 10^6), indicating that it is a strong acid.
- The strength of an acid is also influenced by the polarity of the bond between the hydrogen atom and the halogen atom. The more polar the bond, the stronger the acid.
- In the case of HF, the bond between hydrogen and fluorine is highly polar due to the large electronegativity difference between the two atoms, making HF a weak acid.
- However, in the case of HCl, the bond between hydrogen and chlorine is less polar, resulting in a stronger acid.
- Therefore, option A is not true as HF is a weaker acid compared to HCl.

During its reactions, ozone [1999]
  • a)
    can only combine with hydrogen atoms
  • b)
    accepts electrons
  • c)
    loses electrons
  • d)
    shows the role of electrons to be irrelevant
Correct answer is option 'A'. Can you explain this answer?

Abhijeet Menon answered
Answer:

Ozone (O3) is a molecule composed of three oxygen atoms. It is formed in the atmosphere through a series of chemical reactions involving oxygen molecules (O2) and ultraviolet radiation. Ozone is an important component of the Earth's atmosphere as it plays a crucial role in absorbing harmful ultraviolet (UV) radiation from the sun.

During its reactions, ozone can undergo various processes, including the following:

1. Ozone can combine with hydrogen atoms:
Ozone can react with hydrogen atoms to form water molecules. This reaction is known as hydrogenation, and it occurs under specific conditions. However, it is important to note that ozone can also react with other elements and compounds, not just hydrogen atoms.

2. Ozone accepts electrons:
Ozone is an oxidizing agent, meaning it has the ability to accept electrons from other substances. In many chemical reactions, ozone acts as an electron acceptor, gaining electrons to form stable compounds. This process is part of its role as an oxidant.

3. Ozone loses electrons:
While ozone can accept electrons, it can also lose electrons in certain reactions. When ozone loses an electron, it forms an oxygen molecule (O2). This process is known as reduction, where ozone acts as a reducing agent.

4. The role of electrons is relevant:
The statement that ozone shows the role of electrons to be irrelevant is incorrect. In fact, the role of electrons is crucial in ozone reactions. Electrons are involved in the transfer of charge, which allows ozone to act as an oxidizing or reducing agent. The gain or loss of electrons determines the outcome of the reaction and the formation of new compounds.

In summary, ozone can undergo various reactions, including combining with hydrogen atoms, accepting electrons, and losing electrons. The role of electrons is essential in these reactions, as they determine the behavior of ozone as an oxidizing or reducing agent. Therefore, the correct answer is option 'A' - ozone can only combine with hydrogen atoms.

About 20 km above the earth, there is an ozone layer. Which one of the following statements about ozone and ozone layer is true? [1995]
  • a)
    ozone has a triatomic linear molecule
  • b)
    it is harmful as it stops useful radiation
  • c)
    it is beneficial to us as it stops U.V radiation
  • d)
    conversion of O3 to O2 is an endothermic reaction
Correct answer is option 'C'. Can you explain this answer?

Mehul Choudhary answered
Understanding the Ozone Layer
The ozone layer plays a crucial role in protecting life on Earth. It is located about 20 km above the surface and absorbs most of the sun's harmful ultraviolet (UV) radiation.
Why Statement C is Correct
- Protection from UV Radiation: Ozone (O3) molecules effectively absorb UV radiation, particularly the more harmful UV-B and UV-C types. This absorption prevents these rays from reaching the Earth's surface, reducing the risk of skin cancer, cataracts, and other health issues in humans.
- Environmental Benefits: By filtering out harmful UV radiation, the ozone layer also protects ecosystems, including phytoplankton in oceans, which are vital for the marine food web and global oxygen production.
Why Other Statements are Incorrect
- Statement A (Triatomic Linear Molecule): Ozone is a triatomic molecule, but it is not linear; it has a bent molecular geometry due to the arrangement of its oxygen atoms.
- Statement B (Harmful as it Stops Useful Radiation): While ozone does absorb UV radiation, it does not stop all useful radiation. It selectively filters out harmful UV rays while allowing visible light to pass through, which is essential for life.
- Statement D (Endothermic Reaction): The conversion of O3 to O2 is actually an exothermic reaction, releasing energy. This process occurs naturally in the atmosphere and is crucial for maintaining the balance of ozone.
Conclusion
In summary, the ozone layer is beneficial as it protects living organisms from harmful UV radiation, making option C the correct statement regarding ozone and its layer.

Which of the following oxides will be the least acidic?[1996]
  • a)
    As4O6
  • b)
    As4O10
  • c)
    P4O10
  • d)
    P4O6
Correct answer is option 'A'. Can you explain this answer?

Dipanjan Chawla answered
As th e O.N of the central atom of the compounds increases acidic strength of that compound also increases and on moving from top to bottom in groups acidic strength of oxides also decrease due to decreasing electronegativity in groups.

The correct order of increasing bond angles in the following species are : [2010]
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'C'. Can you explain this answer?

Yash Saha answered
The correct order of increasing bond angle is   
* In ClO2– there are 2 lone pairs of electrons present on the central chlorine atom. Therefore the bond angle in ClO2– is less than 118° which is the bond angle in ClO2 which has less number of electrons on chlorine.

Which one is the correct order of the size of iodine species? [1997]
  • a)
    I > I+ > I–
  • b)
    I > I– > I+
  • c)
    I+ > I– > I
  • d)
    I– > I > I+
Correct answer is option 'D'. Can you explain this answer?

Ayush Sengupta answered
We know that positive ion is always smaller and negative ion is always larger than the corresponding atom. Therefore the correct order of the size is I- > I > I+

Which of the following oxide is amphoteric ?
  • a)
    SnO2
  • b)
    CaO [2011 M]
  • c)
    SiO2
  • d)
    CO2
Correct answer is option 'A'. Can you explain this answer?

Bhargavi Choudhury answered
SnO2 is an amphoteric oxide because it reacts with acids as well as bases to form corresponding salts.

 The structural formula of hypophosphorous acid is
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'A'. Can you explain this answer?

Palak Khanna answered
We know that empirical formula of hypophosphorus acid is H3PO2. In this only one ionisable hydrogen atom is present i.e. it is monobasic. Therefore option (1) is correct structural formula of it.

A certain compound (X) when treated with copper sulphate solution yields a brown precipitate. On adding hypo solution, the precipitate turns white.The compound is
  • a)
    K2CO3
  • b)
    KI [1994]
  • c)
    KBr
  • d)
    K3PO4
Correct answer is option 'B'. Can you explain this answer?

Anand Jain answered
KI reacts with CuSO4 solution to produce cuprous iodide (white precipitate) and I2 (which gives brown colour) Iodine reacts with hypo (Na2S2O35H2O) solution.
Decolourisaiton of solution shows the appearance of white precipitate.

Match List - I (substan ces) with List - II (processes) employed in the manufacture of the substances and select the correct option. [2010]

  • a)
    a
  • b)
    b
  • c)
    c
  • d)
    d
Correct answer is option 'A'. Can you explain this answer?

Maya Sengupta answered
(a) Sulphuric acid (iv) Contact process
(b) Steel (ii) Bessemer ’s process
(c) Sodium hydroxide(iii) Leblanc process
(d) Ammonia (i) Haber ’s process
∴ Correct choice : (a)

HI can be prepared by all the following methods, except[1994]
  • a)
    PI3 + H2O
  • b)
    KI + H2SO4
  • c)
  • d)
    I2 + H 2S
Correct answer is option 'B'. Can you explain this answer?

Pooja Choudhary answered
HI cannot be prepared by heating iodides with concentrated H2SO4 because HI is a strong reducing agent and reduce H2SO4 to SO2 and get themselves oxidised to iodide.

Which among the following is paramagnetic ? [1994]
  • a)
    Cl2O
  • b)
    ClO2
  • c)
    Cl2O7
  • d)
    Cl2O6
Correct answer is option 'B'. Can you explain this answer?

Akshat Chavan answered
ClO2 contain s 7 + 12 i.e. 19 electr ons (valence) which is an odd number, i.e. there is (are) free electron(s). Hence it is paramagnetic in nature.

Which of the following structures is the most preferred and hence of lowest energy for SO3 ? [2011 M]
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'D'. Can you explain this answer?

Maya Sengupta answered
Formal charges help in the selection of the lowest energy structure from a number of possible Lewis structures for a given compound. The lowest energy structure means the structure with the smallest formal charge on each atom of the compound. A Lewis dot structure is preferable when all formal charges are zero.

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