Chemical Bonding and Molecular Structure Test 40

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Chemical Bonding and Molecular Structure Test 40

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Weekly Quiz Competition

Question 1
1 / -0

Which molecule contains both polar and nonpolar covalent bond?

A
$$NH_4Cl$$

B
$$HCN$$

C
$$CH_4$$

D
$$H_2O_2$$

Solution

Polarity is resulting from unequal sharing of electrons. There are three sigma bonds present in hydrogen peroxide. Two of them are between hydrogen and oxygen atoms which is polar in nature. The other one is between two oxygen atoms where there is no unequal sharing of electrons as they have same dipole moment. So it is non polar. So the correct answer is hydrogen peroxide.
Question 2
1 / -0

Which of the following statement is correct?

A
Sigma bond is weaker than pie-bond

B
$$HF$$ is less polar than $$HI$$

C
In $$NH^+_4$$ ions $$4$$ coordinate bond is present

D
In $$SF_6$$ all $$S-F$$ bond length are same

Solution

In $${ SF }_{ 6 }$$, all the $$S-F$$ bonds are equivalent and all bonds are of the same length.
The sigma bond is stronger than the pi-bond. This is because in sigma bond co-axial bonding overlap of the orbital takes place whereas in a pi-bond lateral overlapping of the orbital takes place.
$$HF$$ is more polar than the $$HI$$ as the electronegativity difference between $$H$$ and $$F$$ is more than $$H$$ and $$I$$.
In $$NH_4^+$$, there is only one coordination bond between $$H_3N:$$ and $$H^+$$.
Question 3
1 / -0

Minimum dipole moment containing compound is:

A

B

C

D

Solution
Question 4
1 / -0

In which of the following molecules, the bond lengths around the central atoms are not equal?

A
$$SF_6$$

B
$$PF_5$$

C
$$PCl_3$$

D
$$BF_3$$

Solution

$$SF_{6}$$ has $$sp^{3}d^{2}$$ hybridisation, $$BF_{3}$$ has $$sp^{2}$$ hybridisation. In all of these , the bond lengths are equal. However, $$PF_{5}$$ has $$sp^{3}d$$ hybridization i.e. trigonal bi-pyramidal structure. In the triagonal plane, the bond angle is $$120^{\circ}$$ whereas the angle between the pyramidal bond and the plane is $$90^{\circ}$$
From the figure, we can say that it experiences different $$bp-bp$$ repulsion , due to which all the bond lengths are not equal.
Question 5
1 / -0

In the given reaction:
$${ \left[ Co{ \left( { NH }_{ 3 } \right) }_{ 5 }{ H }_{ 2 }O \right] }^{ 2+ }+{ NH }_{ 3 }\longrightarrow compound(Y)+{ e }^{ - }+{ H }_{ 2 }O$$
Compound (X)
Number of unpaired electron in compound X and compound Y are respectively:

A
$$(1,0)$$

B
$$(3,1)$$

C
$$(1,3)$$

D
$$(3,3)$$

Solution

$${ \left[ Co{ \left( { NH }_{ 3 } \right) }_{ 5 }{ H_2O } \right] }^{ 2+ }\rightarrow { d }^{ 7 }$$
$$\left( X \right) $$ $$\rightarrow $$ low spin
$$\rightarrow $$ No. of unpaired $${ e }^{ - }=1$$
$${ \left[ { \left( { Co(NH }_{ 3 })_6\right) }\right] }^{ 3+ }\rightarrow { d }^{ 6 }$$
$$\left( Y \right) $$ $$\rightarrow $$ low spin
$$\rightarrow $$ No. of unpaired $${ e }^{ - }=0$$
Question 6
1 / -0

Which conformation has non-zero dipolemoment?

A

B

C

D

Solution

In para-dihydroxybenzene or para-hydroxyphenol the dipole moment is not along $$-C-O$$ axis, but rather at some angle to that axis, so that group substituents at opposite directions in the ring, do not oppose the bond moments directly.
The $$C-O-H$$ bond angle is close to $$90^o$$ . Arrangement of H is not symmetrical about the line of attachment of the group.
Question 7
1 / -0

The total number of lone pairs of electrons in $$N_2O_3$$ is:

A
6

B
8

C
5

D
none of these

Solution

$${ N }_{ 2 }{ O }_{ 3 }$$ has $$'8'$$ lone pair according to its structure.
Question 8
1 / -0

The compound with no dipole moment is:

A
methyl chloride

B
carbon tetrachloride

C
methylene chloride

D
chloroform

Solution

In $${ CCl }_{ 4 }$$
The Chlorines are electron withdrawing groups and $$CCl_4$$ is symmetric molecule. One side cancels the other side dipole moment. So dipole moment is zero.
Question 9
1 / -0

Which of the following molecules\ions does not contain unpaired electrons?

A
$$N^+_2$$

B
$$O_2$$

C
$$O^{2-}_2$$

D
$$B_2$$

Solution

The molecular orbital diagram of $${ O }_{ 2 }^{ -2 },{ \pi }^{ \ast }2Px$$ and $${ \pi }^{ \ast }2Py$$ molecular orbitals are completely filled , which are partially filled in $${ O }_{ 2 }$$. These are no unpaired electrons. So, $${ O }_{ 2 }^{ -2 }$$ does not contain unpaired electrons.
Question 10
1 / -0

Arrange the following compounds in order of increasing dipole moment :

Toluene (I)
m- dichlorobenzene (II)
o-dichlorobenzene (III)
p- dichlorobenzene (IV)

A
I < IV < II < III

B
IV < I < II < III

C
IV < I < III < II

D
IV < II < I < III

Solution