An element belongs to group-15 and 3rd period of the periodic table. Its electronic configuration would be :
a.
1s^2 2s^2 2p^6 3s^2 3p^2
b.
1s^2 2s^2 2p^4
c.
1s^2 2s^2 2p^6 3s^2 3p^3
Correct Answer
d.
1s^2 2s^2 2p^3
Step-by-Step AI Explanation
Verified Method
Elements in group 15 have the valence shell configuration $ns^2 np^3$. The 3rd period indicates the principal quantum number $n=3$. Therefore, the valence shell configuration is $3s^2 3p^3$. Adding the core electrons ($1s^2 2s^2 2p^6$), the full configuration is $1s^2 2s^2 2p^6 3s^2 3p^3$. Choice (A) corresponds to Silicon (Group 14), (B) is Oxygen (Period 2), and (D) is Nitrogen (Period 2).
Q2mcq1 mark
Bauxite has the composition :
a.
Al_2O_3 · nH_2O
Correct Answer
b.
Fe_2O_3 · 2H_2O
c.
Al_2O_3
d.
None of the above
Step-by-Step AI Explanation
Verified Method
Bauxite is the principal ore of aluminium and is represented by the formula $Al_2O_3 \cdot nH_2O$. It typically contains varying amounts of water. $Al_2O_3$ (anhydrous) is Corundum, and $Fe_2O_3 \cdot nH_2O$ is Limonite.
Q3mcq1 mark
If 75% of a first order reaction was completed in 60 min, 50% of the same reaction under the same conditions would be completed in :
a.
35 minutes
b.
20 minutes
c.
75 minutes
d.
30 minutes
Correct Answer
Step-by-Step AI Explanation
Verified Method
For a first-order reaction, the rate constant $k = \frac{2.303}{t} \log(\frac{[A]_0}{[A]_t})$. When 75% is completed, $[A]_t = 0.25[A]_0$, so $k = \frac{2.303}{60} \log(4) = \frac{2.303}{60} \times 0.602$. The half-life $t_{1/2} = \frac{0.693}{k}$. Substituting $k$, we get $t_{1/2} = \frac{0.693 \times 60}{2.303 \times 0.602} \approx 30$ minutes.
Q4mcq1 mark
Which of the following reagent can be used to convert nitrobenzene to aniline ?
a.
ZnHg/NaOH
b.
Zn/NH_4Cl
c.
Sn/HCl
Correct Answer
d.
All of these
Step-by-Step AI Explanation
Verified Method
Nitrobenzene can be reduced to aniline (amino benzene) using metal-acid combinations like $Sn/HCl$, $Fe/HCl$, or $Zn/HCl$ (catalytic hydrogenation is also possible). $Sn/HCl$ is the standard laboratory method. $Zn/NH_4Cl$ is typically used to stop at the intermediate phenylhydroxylamine stage, and $ZnHg/NaOH$ is a Clemmensen reduction condition usually reserved for carbonyls.
Q5mcq1 mark
HO-CH_2-CH_2-OH on heating with periodic acid gives :
a.
Methanal
Correct Answer
b.
Methanoic acid
c.
CO_2
d.
Glyoxal
Step-by-Step AI Explanation
Verified Method
Periodic acid ($HIO_4$) cleaves 1,2-diols (vicinal diols) at the C-C bond. For ethylene glycol ($HO-CH_2-CH_2-OH$), the cleavage results in two molecules of formaldehyde ($CH_2O$ or methanal).
Q6mcq1 mark
A complex in which the oxidation number of the metal is zero is :
a.
K_4[Fe(CN)_6]
b.
[Fe(CN)_3(NH_3)_3]
c.
[Fe(CO)_5]
Correct Answer
d.
Both (b) and (c)
Step-by-Step AI Explanation
Verified Method
In $[Fe(CO)_5]$, the ligand $CO$ (carbonyl) is neutral (oxidation state 0). Since the complex is neutral, the oxidation state of Fe must be 0. In $K_4[Fe(CN)_6]$, Fe is +2. In $[Fe(CN)_3(NH_3)_3]$, the charge balance implies a non-zero oxidation state for iron.
Q7mcq1 mark
Which of the following can act as Lowry-Bronsted acid as well as base ?
a.
HPO_4^{2-}
Correct Answer
b.
HCl
c.
Br^-
d.
SO_4^{2-}
Step-by-Step AI Explanation
Verified Method
A Lowry-Bronsted acid can donate a proton, and a base can accept one. $HPO_4^{2-}$ can donate a proton to become $PO_4^{3-}$ (acting as an acid) or accept a proton to become $H_2PO_4^-$ (acting as a base). The others like $HCl$ only act as acids, and $Br^- / SO_4^{2-}$ typically act as conjugate bases.
Q8mcq1 mark
An aqueous solution of borax is :
a.
basic
Correct Answer
b.
neutral
c.
amphoteric
d.
acidic
Step-by-Step AI Explanation
Verified Method
Borax ($Na_2B_4O_7 \cdot 10H_2O$) dissolves in water to form orthoboric acid ($H_3BO_3$, a weak acid) and sodium hydroxide ($NaOH$, a strong base). The hydrolysis results in an alkaline (basic) solution.
Q9mcq1 mark
Which one of the following is an example for homogeneous catalysis ?
a.
Hydrogenation of oil
b.
Manufacture of ammonia by Haber’s process
c.
Hydrolysis of sucrose in presence of dil.HCl
Correct Answer
d.
Manufacture of sulphuric acid by Contact process
Step-by-Step AI Explanation
Verified Method
Homogeneous catalysis occurs when the catalyst and the reactants are in the same phase. In the hydrolysis of sucrose (aqueous) in the presence of dilute HCl (aqueous), both are in the liquid phase. Hydrogenation of oil (A), Haber's process (B), and Contact process (D) are examples of heterogeneous catalysis because the catalysts are solid while reactants are gas or liquid.
Q10mcq1 mark
The formation of cyanohydrin from acetone is an example of :
a.
electrophilic addition
b.
nucleophilic substitution
c.
nucleophilic addition
Correct Answer
d.
electrophilic substitution
Step-by-Step AI Explanation
Verified Method
The formation of cyanohydrin from acetone involves the attack of the cyanide ion (a nucleophile) on the electrophilic carbonyl carbon of the acetone. This is a characteristic nucleophilic addition reaction of carbonyl compounds.
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