FBISE Class 9th (SSC-l)
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FBISE Class 9th (SSC-l)
Answer: Bond length increases as bond order decreases: C-C triple bond (C2H2) < C=C double bond (C2H4) < C-C single bond (C2H6).
Answer: Alizarin is a mordant dye that requires a metallic mordant (like aluminum hydroxide) to bind to fabric, producing a vivid red color.
Answer: Water has sp3 hybridization with two bonding pairs and two lone pairs. The lone pair repulsion compresses the H-O-H angle from 109.5 to about 104.5 degrees.
Answer: Acidic strength of hydrohalic acids increases down the group (HCl < HBr < HI) because bond dissociation energy decreases as atomic size increases.
Answer: Molar mass of H2O = 18 g/mol. Moles = 36/18 = 2 moles.
Answer: NO2- is an ambidentate ligand that can bind through N or O. This gives rise to linkage isomerism: -NO2 (nitro) vs -ONO (nitrito).
Answer: BF3 has three bonding pairs and no lone pairs on boron, requiring sp2 hybridization and trigonal planar geometry.
Answer: Sodium (Na) is a strong reducing agent because it readily loses its valence electron to form Na+, getting oxidized in the process.
Answer: XeF4 has sp3d2 hybridization with 4 bonding pairs and 2 lone pairs. The lone pairs are trans to each other, giving square planar geometry.
Answer: CH3CH(OH)COOH (lactic acid) has a chiral carbon bonded to four different groups (-H, -OH, -CH3, -COOH), exhibiting optical isomerism.
Answer: pH = pKa + log([salt]/[acid]). When [salt] = [acid], pH = pKa = -log(1.8 x 10^-5) = 4.74.
Answer: In hydrogen (single electron system), energy depends only on n. 3s has n=3, which is higher than n=2 (2s, 2p) and n=1 (1s).
Answer: Potassium permanganate has the formula KMnO4, where Mn is in the +7 oxidation state and is a powerful oxidizing agent.
Answer: Iron (Fe, Z=26) has partially filled 3d orbitals ([Ar] 3d6 4s2), placing it in the d-block of the periodic table.
Answer: CaCO3 decomposes as: CaCO3 -> CaO + CO2. One mole of CaCO3 produces exactly one mole of CO2.
Answer: Copper is an exception to the expected configuration. One 4s electron is promoted to 3d to achieve a fully filled 3d10 subshell for extra stability.
Answer: H-Cl has an electronegativity difference of 0.9, resulting in unequal electron sharing (polar covalent bond). Na-Cl is ionic, and H-H and O-O are nonpolar.
Answer: Magnesium (Mg) loses its two valence electrons to achieve a stable neon-like configuration, forming Mg2+ with a +2 charge.
Answer: CH3OCH3 (dimethyl ether) has an oxygen atom bonded between two alkyl groups (R-O-R\'), which defines the ether functional group.
Answer: By convention, the standard enthalpy of formation of any element in its most stable standard state is defined as zero.