Chemistry Test 74

Autoxidation is any oxidation that occurs in presence of oxygen. The term is usually used to describe the degradation of organic compounds in air (as a source of oxygen). Autoxidation produces hydroperoxides i.e. formation of H₂O by the oxidation of H₂O₂, and cyclic organic peroxides. These species can react further to form many products. The process is relevant to many phenomena including aging, paint, and spoilage of foods, degradation of petrochemicals, and the industrial production of chemicals. Autoxidation is important because it is a useful reaction for converting compounds to oxygenated derivatives, and also because it occurs in situations where it is not desired (as in the destructive cracking of the rubber in automobile tires or in rancidification).

Hence, the correct option is (A).

As we move down the group in the Periodic Table from F to I, the electronegativity of halogen decreases, therefore the polarity of the CX bond and hence the dipole moment of the haloalkane should also decrease accordingly. But the dipole moment of CH3F is slightly lower than that of CH₃Cl. The reason being that although the magnitude of the -ve charge on the F atom is much higher than that on the Cl atom but due to the small size of F as compared to Cl, the CF bond distance is so small that the product of charge and distance (μ=q×d), ie, the dipole moment of CH3F turns out to be slightly lower than that of CH₃Cl.

Therefore, the order of the dipole moment is CH₃Cl > CH₃ F > CH₃Br

Hence, the correct option is (C).

The number of isomeric forms that are represented by C₇H₉N is 5. They can be represented as:

Hence, the correct option is (B).

Very simple, as +I groups are attached to a carboxylic acid, the acidic nature decreases. As the size of +I groups increases, the acidity decreases proportionally. Whereas the -I groups enhance the acidity. As in alcohols, the acidity is dependent on the same factors in the same way but compared to carboxylic acids, alcohols are less acidic due to their weak alkoxide ion (RO-). As the aromatic groups are connected, the acidic nature is enhanced due to resonance. So an aromatic carboxylic acid is more acidic than its aliphatic counterpart.

The order of acidity therefore is,

4 > 3 > 1 > 5 > 2

Hence, the correct option is (C).

The oxidation number of cobalt in the complex [Co(NH₃)₆]Cl₃ is +3. It can be calculated as:

Let the oxidation number be x of cobalt:

 x + 6(0) =+3 

∴ No. of Co in complex ion = +3

Hence, the correct option is (B).

The effects of the thyroid come from two iodine containing-hormones, triiodothyronine (T₃), and thyroxine (T₄). Iodine (atomic number, 53; standard atomic mass, 126.9) is a rate-limiting element for the synthesis of thyroid hormones.

Hence, the correct option is (C).

Hybridization = a rounded atoms to central atom + 1/2 (valence e- of central atom -bonded e-)

So, hybridization of XeF6 = 6 + 1/2 (8−6) = 7

i.e. 7= (bonded electron)+ (Lone pair)

So, hybridization =7 = sp³⁡d³

Its hybridization is sp³d³ however its geometry is capped or distorted octahedral(square bipyramidal) one and not pentagonal bipyramidal. The fluorine atoms occupy the vertices of the octahedron and lone pairs keep on moving in space to minimize repulsion, and hence distorting the octahedral geometry. 

Hence, the correct option is (B).

Percent ionic character for HCI molecule is 17.2%

Using electron negativity values the percentage ionic character could be calculated as:

percent ionic character =16(ΔE)+3.5(ΔE)²

where, ΔE is the electron negativity difference of two atoms.

electron negativity of H is 2.1 and for Cl it is 3.0.

So, ΔE=3.0−2.1=0.9

Let's plug in this value in the formula:

percent ionic character =16(0.9)+3.5(0.9)²

percent ionic character =14.4+2.835=17.2

Therefore, the percent ionic character for the HCI molecule is 17.2%  ionic.

Hence, the correct option is (A).