Chemistry Q135 – AP-EAMCET 2025

Home Chemistry Basic ChemistryQuestion #31

Consider the following Statement-I : The products formed when diborane burns in air are

B_{2} O_{3}

H_{2}

and

O_{2}

. Statement-II : Hybridization of boron atom in orthoboric acid is

s p^{2}

. The correct answer is

Clue 1 of 3: Chemical Reactions and Products

Understand the typical products formed when a hydride like diborane burns in air. Combustion reactions usually involve oxygen and produce oxides and water.

🧠 Full Solution Path

Step 1: Analyze Statement-I (Combustion of Diborane)✦ Active

Diborane ( $B_{2} H_{6}$ ) is a hydride of boron. When it burns in air (reacts with oxygen, $O_{2}$ ), it undergoes a combustion reaction. The typical products of combustion for compounds containing boron and hydrogen are boron oxide and water.

B_{2} H_{6} (g) + 3 O_{2} (g) \to B_{2} O_{3} (s) + 3 H_{2} O (g)

The statement claims the products are $B_{2} O_{3}$ , $H_{2}$ , and $O_{2}$ . This is incorrect as water ( $H_{2} O$ ) is formed, not hydrogen gas ( $H_{2}$ ), and oxygen ( $O_{2}$ ) is a reactant, not a product. Therefore, Statement-I is incorrect.

💡 Teacher's Secret Hint

Remember that combustion reactions involving hydrogen-containing compounds typically produce water, not elemental hydrogen.

Step 2: Analyze Statement-II (Hybridization of Boron in Orthoboric Acid)○ Expand

Orthoboric acid has the chemical formula $H_{3} B O_{3}$ . The central atom is boron (B). Boron is bonded to three hydroxyl (-OH) groups.

To determine the hybridization, we count the number of sigma bonds and lone pairs around the central boron atom. In $H_{3} B O_{3}$ , boron forms three single bonds with three oxygen atoms (from the -OH groups) and has no lone pairs.

Steric Number = (Number of sigma bonds) + (Number of lone pairs)

Steric Number for B in H_{3} B O_{3} = 3 + 0 = 3

A steric number of 3 corresponds to $s p^{2}$ hybridization and a trigonal planar geometry. Therefore, Statement-II is correct.

💡 Teacher's Secret Hint

For main group elements, the steric number directly correlates with hybridization: 2 = $s p$ , 3 = $s p^{2}$ , 4 = $s p^{3}$ .

Step 3: Conclude based on Statement Analysis○ Expand

Statement-I is incorrect, and Statement-II is correct.

This matches option 4: "Statement-I is not correct, but statement-II is correct".

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Chemistry Question 135 – AP-EAMCET 2025

Clue 1 of 3: Chemical Reactions and Products

🧠 Full Solution Path