p-Block Elements Questions — NEET Chemistry

Q1

Which one of the following reactions does NOT belong to Lassaigne's test?

A

\mathrm{Na}+\mathrm{X} \xrightarrow[\Delta]{ }+\mathrm{NaX}

B

2 \mathrm{CuO}+\mathrm{C} \xrightarrow[\Delta]{ } 2 \mathrm{Cu}+\mathrm{CO}_2

C

\mathrm{Na}+\mathrm{C}+\mathrm{N} \underset{\Delta}{\longrightarrow} \mathrm{NaCN}

D

2 \mathrm{Na}+\mathrm{S} \underset{\Delta}{\longrightarrow} \mathrm{Na}_2 \mathrm{~S}

Correct Answer

Option B

Solution

Nitrogen, sulphur, halogens and phosphorus present in an organic compound are detected by Lassaigne's test.

\begin{aligned} & \mathrm{Na}+\mathrm{C}+\mathrm{N} \xrightarrow{\Delta} \mathrm{NaCN} \\ & 2 \mathrm{Na}+\mathrm{S} \xrightarrow{\Delta} \mathrm{Na}_2 \mathrm{~S} \\ & \mathrm{Na}+\mathrm{X} \xrightarrow{\Delta} \underset{(\mathrm{X}=\mathrm{Cl}, \mathrm{Br}, \mathrm{l})}{\mathrm{NaX}} \end{aligned}

Q2

Which one of the following statements is correct?

A All enzymes that utilise ATP in phosphate transfer require

\mathrm{Ca}

as the cofactor.

B The bone in human body is an inert and unchanging substance.

C

\mathrm{Mg}

plays roles in neuromuscular function and interneuronal transmission.

D The daily requirement of

\mathrm{Mg}

and

\mathrm{Ca}

in the human body is estimated to be 0.2 - 0.3

\mathrm{g}

.

Correct Answer

Option D

Solution

The daily requirement in the human body has been estimated to be 200-300 mg (NCERT : s-block) Biological importance of magnesium and calcium.

Q3

Weight (g) of two moles of the organic compound, which is obtained by heating sodium ethanoate with sodium hydroxide in presence of calcium oxide is :

A 32

B 30

C 18

D 16

Correct Answer

Option A

Solution

Weight

=2\times16=32

g

Q4

The element used for welding metals with high melting points is

A He

B Cl 2

C H 2

D Ne

Correct Answer

Option C

Solution

Atomic hydrogen atoms produced by dissociation of dihydrogen with the help of electric arc use for cutting and welding metals with high melting points.

Q5

CaCl 2 and Ca(OCl) 2 are components of

A Lime water

B Gypsum

C Portland cement

D Bleaching powder

Correct Answer

Option D

Solution

Milk of lime reacts with chlorine to form hypochlorite, a constituent of bleaching powder 2Ca(OH) 2 + 2Cl 2 $\to$

\mathop {\mathrm{CaC{l_2} + Ca{{(OCl)}_2}}}\limits_{\mathrm{Bleaching\,Powder}}

+ 2H 2 O

Q6

Which one of the following is not a calcination reaction?

A CaCO 3 + 2HCl

\overset{\Delta}\longrightarrow

CaCl 2 + H 2 O + CO 2

B ZnCO 3

\overset{\Delta}\longrightarrow

ZnO + CO 2

C Fe 2 O 3 . xH 2 O

\overset{\Delta}\longrightarrow

Fe 2 O 3 + xH 2 O

D CaCO 3 . MgCO 3

\overset{\Delta}\longrightarrow

CaO + MgO + 2CO 2

Correct Answer

Option A

Solution

Calcination involves heating when the volatile matter escapes leaving behind the metal oxide. Fe 2 O 3 . xH 2 O(s)

\overset{\Delta}\longrightarrow

Fe 2 O 3 (s) + xH 2 O(g) ZnCO 3 (s) $\to$ ZnO(s) + CO 2 (g) CaCO 3 .

MgCO 3 (s) $\to$ CaO(s) + MgO(s) + 2CO 2 (g) CaCO 3 + 2HCl

\overset{\Delta}\longrightarrow

CaCl 2 + H 2 O + CO 2 Not calcination It is a neutralization reaction.

Q7

Identify the incorrect statement from the following

A Alkali metals react with water to form their hydroxides.

B The oxidation number of K in KO 2 is +4.

C Ionisation enthalpy of alkali metals decreases from top to bottom in the group.

D Lithium is the strongest reducing agent among the alkali metals.

Correct Answer

Option B

Solution

$\bullet$ Alkali metals show only '+1' oxidation state in all of their compounds. KO 2 is a super-oxide in which O

_2^ -

is anion and K + is cation oxidation state of K is +1.

Q8

Among the following alkaline earth metal halides, one which is covalent and soluble in organic solvents is :

A Beryllium chloride

B Calcium chloride

C Strontium chloride

D Magnesium chloride

Correct Answer

Option A

Solution

$\bullet$ Except for beryllium chloride all other chloride of alkaline earth metals are ionic in nature.

$\bullet$ Due to small size of Be, Beryllium chloride is essentially covalent and soluble in organic solvents.

Q9

The structures of beryllium chloride in solid state and vapour phase, are :

A Chain in both

B Chain and dimer, respectively

C Linear in both

D Dimer and Linear, respectively

Correct Answer

Option B

Solution

Beryllium chloride has a chain structure in the solid state as shown below In vapour phase Beryllium chloride tends to form a chloro-bridged dimer.

Q10

The following metal ion activities many enzymes, participates in the oxidation of glucose to produce ATP and with Na, is responsible for the transmission of nerve signals.

A Copper

B Calcium

C Potassium

D Iron

Correct Answer

Option C

Solution

Potassium (K) activities many enzymes participate in the oxidation of glucose to produce ATP and helps in the transmission of nerve signal along with Na.