Question 1

Which of the following elements belongs to the s-block of the periodic table?

Accepted Answer

Sodium is an alkali metal in Group 1 with its valence electron in the s-orbital, classifying it as an s-block element.

Question 2

What is the electron configuration of Magnesium (Mg)?

Accepted Answer

Magnesium has atomic number 12, with the complete configuration 1s² 2s² 2p⁶ 3s², where the outermost electrons fill the s-orbital.

Question 3

Which property correctly describes the s-block elements?

Accepted Answer

s-block elements (alkali metals and alkaline earth metals) readily lose their valence s-electrons to form positively charged ions and ionic compounds.

Question 4

Which of the following represents the correct order of increasing atomic radius in the s-block?

Accepted Answer

Atomic radius increases down a group in the periodic table; Li (Group 1, Period 2) < Na (Period 3) < K (Period 4).

Question 5

When calcium (Ca) reacts with oxygen (O₂), the product formed is:

Accepted Answer

Calcium, an s-block alkaline earth metal with +2 oxidation state, combines with oxygen's -2 oxidation state to form CaO in a 1:1 molar ratio.

Question 6

Which of the following is the correct order of ionization enthalpy for Group 1 elements (alkali metals)?

Accepted Answer

Ionization enthalpy decreases down Group 1 due to increasing atomic size and electron shielding, so Li has the highest value.

Question 7

When sodium is heated in excess oxygen, the primary product formed is:

Accepted Answer

Sodium reacts with excess oxygen to form sodium peroxide (Na₂O₂), which contains the peroxide ion (O₂²⁻).

Question 8

The solubility of alkaline earth metal hydroxides decreases down the group. The correct order is:

Accepted Answer

Solubility of M(OH)₂ increases down Group 2 as the lattice enthalpy decreases more rapidly than hydration enthalpy, making Ba(OH)₂ most soluble.

Question 9

Potassium superoxide (KO₂) reacts with CO₂ and H₂O in the following manner. What are the products?

Accepted Answer

KO₂ + CO₂ + 2H₂O → K₂CO₃ + H₂O₂ + O₂; this reaction is used in oxygen generation systems.

Question 10

Which alkaline earth metal forms a nitride when heated in nitrogen atmosphere?

Accepted Answer

Magnesium readily reacts with nitrogen when heated to form Mg₃N₂; other alkaline earth metals are less reactive toward nitrogen.

Question 11

The hydration enthalpy of lithium is higher than that of sodium. This is because:

Accepted Answer

Li⁺ is smaller than Na⁺, resulting in higher charge density and stronger electrostatic interactions with water molecules, leading to greater hydration enthalpy.

Question 12

When calcium carbide reacts with water, the main organic product formed is:

Accepted Answer

CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂; calcium carbide is a classic source of acetylene gas.

Question 13

Among the alkali metals, which element shows the most anomalous behavior and why?

Accepted Answer

Lithium exhibits anomalous properties (like forming a nitride and having high hydration enthalpy) due to its small size and high charge density, making it less typical of Group 1 elements.

Question 14

When sodium metal is heated in excess oxygen, the primary product formed is:

Accepted Answer

Sodium burns in excess oxygen to form sodium peroxide (Na₂O₂) as the major product, which contains the O₂²⁻ peroxide ion.

Question 15

The solubility of alkaline earth metal hydroxides in water decreases down the group. Which of the following correctly orders these hydroxides by solubility (highest to lowest)?

Accepted Answer

Solubility of alkaline earth metal hydroxides decreases down Group 2 due to increasing hydration enthalpy being outweighed by the lattice enthalpy effect, making Be(OH)₂ most soluble and Ba(OH)₂ least soluble.

Question 16

Which of the following statements about the diagonal relationship between lithium and magnesium is correct?

Accepted Answer

The diagonal relationship shows Li and Mg both form hydrated chlorides due to high charge density of Li⁺ and Mg²⁺ ions, causing strong polarization of water molecules and hygroscopic behavior.

CDS s-Block Elements

s-Block Elements — Practice Questions