FBISE Class 9th (SSC-l)
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FBISE Class 9th (SSC-l)
Answer: A buffer consists of a weak acid (CH3COOH) and its conjugate base (CH3COO- from CH3COONa), which resists pH changes.
Answer: C4H10 has two structural isomers: n-butane (straight chain) and isobutane (2-methylpropane, branched).
Answer: SF6 has sulfur bonded to 6 fluorine atoms with no lone pairs, requiring sp3d2 hybridization and octahedral geometry.
Answer: Aluminum is extracted from molten Al2O3 (dissolved in cryolite) by electrolysis in the Hall-Heroult process due to its high reactivity.
Answer: Na2SO4 dissociates into 2Na+ and SO42-, producing 3 ions per formula unit, so i = 3.
Answer: The double bond starts at carbon 2 in the four-carbon chain, so the IUPAC name is but-2-ene.
Answer: CCl4 has a tetrahedral geometry with four identical C-Cl bonds. The bond dipoles cancel out, making the molecule nonpolar.
Answer: At STP (0 degrees C, 1 atm), 1 mole of an ideal gas occupies 22.4 liters according to Avogadro\'s law.
Answer: AlCl3 has an incomplete octet on aluminum, allowing it to accept an electron pair, which defines a Lewis acid.
Answer: C6H4Cl2 has three positional isomers: 1,2-dichlorobenzene (ortho), 1,3-dichlorobenzene (meta), and 1,4-dichlorobenzene (para).
Answer: Electronegativity generally increases across a period because effective nuclear charge increases, attracting bonding electrons more strongly.
Answer: H3PO4 is triprotic (3 replaceable H+ ions). Normality = Molarity x n-factor = 1 x 3 = 3 N.
Answer: Nylon-6,6 is formed by condensation of adipic acid and hexamethylenediamine with loss of water, making it a condensation polymer.
Answer: In peroxides (like H2O2 and Na2O2), oxygen has an oxidation state of -1 because the O-O bond involves shared electrons equally.
Answer: Mg has a stable 3s2 fully filled subshell, making its first ionization energy higher than Na (3s1), Al (3s2 3p1), and Si (3s2 3p2).
Answer: Water has two O-H bonds and two lone pairs on oxygen, giving it a bent molecular geometry.
Answer: Ethene (an alkene with a C=C double bond) undergoes addition reactions because the pi bond is relatively weak and can be broken to add atoms.
Answer: Moles of NaCl = 5.85/58.5 = 0.1 mol. Molarity = 0.1 mol / 0.5 L = 0.2 M.
Answer: CaO is a basic oxide formed from a metal (Ca). It reacts with water to form Ca(OH)2 and with acids to form salts.
Answer: Cl has 7 valence electrons. Three are used for bonding with F, leaving 4 electrons = 2 lone pairs, giving a T-shaped molecular geometry.