Tag: chemistry

Questions Related to chemistry

Two compounds of A and B have similar formula $AX _3$ and $BX _3$ respectively. But, the compound of A has the dipole moment and dipole moment of the compound of B is zero. Which of the following statements is true regarding compounds of A & B?

chemistry chemical bond and chemical equation properties of covalent compounds types of bonds and properties covalent bond

  1. A and B are iso structural.

  2. A may have lone pair on central atom whereas B has no lone pair.

  3. A and B differ wrt type of hybridisation of central atom.

  4. All the above.

Show answer
Correct Option: C
Explanation:

A and B differ wrt type of hybridization of central atom. 'B' may have lone pair on central atom whereas 'A' has no lone pair.
'A' has dipole moment as it is trigonal planar in which individual bond dipoles cancel each other and dipole moment of 'B' is zero as it has pyramidal geometry in which individual bond dipoles do not cancel each other. 

Assertion : $CH _3Cl$ is a polar molecule.
Reason : The Lewis diagram of polar molecules always has at least one lone pair of electrons.

chemistry chemical bond and chemical equation properties of covalent compounds types of bonds and properties covalent bond

  1. Assertion and Reason  are correct and Reason  is the correct explanation of Assertion 

  2. Both the Assertion and Reason are correct and Reason  is not the correct explanation of Assertion 

  3. Assertion is correct but Reason is not correct

  4. Assertion is not correct but Reason is correct

  5. Both the Assertion and Reason are not correct

Show answer
Correct Option: C
Explanation:

Compound in statement 1 must be $C{ H } _{ 3 }Cl$.Since carbon,hydrogen and chlorine have different electronegativity,the bonds are polar in nature. Moreover, there is symmetry in the structure of the molecule, so there is a net dipole moment hence it is a polar molecule.

It is not a necessary condition that there has to at least one lone pair of electrons for a molecule to be polar. $C{ H } _{ 3 }Cl$ is an example.

Which of the following statements is/are true?

chemistry chemical bond and chemical equation properties of covalent compounds types of bonds and properties covalent bond

  1. Covalent bonds are directional.

  2. Ionic bonds are non-directional.

  3. A polar bond is formed between two atoms which have the same electronegativity value.

  4. The presence of polar bonds in a polyatomic molecule suggests that it has zero dipole moment.

Show answer
Correct Option: A,B
Explanation:

Covalent bonds are directional and ionic bonds are nondirectional. A polar bond is formed between two atoms which have different electronegativity value. The presence of polar bonds in a polyatomic molecule suggests that mostly it has non-zero dipole moment.

$A,\ B,\ C$ are three substances. $A$ does not conduct electricity in the solid, molten state and aqueous solution. $B$ conducts electricity both in the fused and aqueous states, while $C$ conducts electricity only in the aqueous state. In solid state neither $B$ nor $C$ conducts electricity. Which of the following statements is/are true regarding $A,\ B$ and $C $?

chemistry chemical bond and chemical equation properties of covalent compounds types of bonds and properties covalent bond

  1. $A$ has polar covalent linkage

  2. $A$ has non-polar covalent linkage

  3. $B$ is ionic in nature

  4. Cation has polar covalent bonds

Show answer
Correct Option: B,C,D
Explanation:
$A$ does not conduct electricity in the solid and molten state suggests that $A$ is not an ionic compound and it can be a covalent compound.
$A$ is not conducting electricity in aqueous solution also, it suggests that all the element in compound $A$ has the same electronegativity.
Hence, $A$ can be non-polar covalent compound that means it has non-polar covalent linkage.
$B$ conducts electricity in a fused state and in aqueous states, This represents that the electronegativity difference in the compound is very high.
Hence, $B$ can be an ionic bond
$C$ conducts electricity in only in the aqueous state. It means that $C$ does not conduct electricity in a molten state that means $C$ is not an ionic compound.
It can be a covalent compound and as it is conducting electricity in the aqueous state, there must be small electronegativity difference.
Hence, $C$ can be a polar covalent compound.

Which of the following is not an actinoid?

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. Curium (Z = 96)

  2. Californium (Z = 98)

  3. Uranium (Z = 92)

  4. Terbium (Z = 65)

Show answer
Correct Option: D
Explanation:

Terbium (Z = 65) is a lanthanoid and all others are actinoids. Lanthanoids have atomic numbers from 58 to 71. Actinoids have atomic numbers from 90 to 103.

Identify the incorrect statement among the following. 

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. 4f and 5f orbitals are equally shielded.

  2. 4-Block elements show irregular and erratic chemical properties among themselves.

  3. La and Lu have partially filled d-orbitals and no other partially filled orbitals.

  4. The chemistry of various lanthanoids is very similar.

Show answer
Correct Option: A
Explanation:

4f and 5f orbitals are not equally shielded. 5f are poorly shielded as 5f orbitals are away from the nucleus.

Also, 5f has poor shielding effect than 4f due to the large size of f-orbital, it is more diffused.

Which of the following is not an actinoid ?

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. Am

  2. Cm

  3. Fm

  4. Tm

Show answer
Correct Option: D
Explanation:

LANTHANIDES


58Ce  59Pr  60Nd  61Pm  62Sm  63Eu  64Gd  65Tb  66Dy  67Ho  68Er  69Tm  70Yb  71Lu 

ACTINIDES

 90Th 91 Pa 92 U 93 Np 94 Pu 95 Am 96 Cm 97Bk  98Cf  99Es  100 Fm 101 Md 102No  103Lr 
          

Which of the following is not an actinide ?

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. Curium

  2. Californium

  3. Uranium

  4. Terbium

Show answer
Correct Option: D
Explanation:

LANTHANIDES


58Ce  59Pr  60Nd  61Pm  62Sm  63Eu  64Gd  65Tb  66Dy  67Ho  68Er  69Tm  70Yb  71Lu 

ACTINIDES

 90Th 91 Pa 92 U 93 Np 94 Pu 95 Am 96 Cm 97Bk  98Cf  99Es  100 Fm 101 Md 102No  103Lr 
          

Which of the following elements belongs to actinide series?

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. Lu

  2. Gd

  3. Th

  4. La

Show answer
Correct Option: C
Explanation:

Lu, Gd and La belongs to lanthanide series and Th belongs to actinide series.


Option C is correct.

The first and last elements of actinides are:

chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

  1. Actinium and Thorium

  2. Actinium and Nobelium

  3. Actinium and Mendelevium

  4. Actinium and Lawrencium

Show answer
Correct Option: D
Explanation:

We have 15 elements in actinides. They are from atomic number 89 to 103 Actinium, Thorium, Protactinium, Uranium, Neptunium, Plutonium, Americium, Curium, Berkelium, Californium, Einsteinium, Fermium, Mendelevium, Nobelium, Lawrencium. Hence, from these list we could say that Actinium is the first and Lawrencium is the last element in actinides.