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120 questions · 120 marks · 2 hours
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Correct answer: (B) K = ½mv²
Kinetic energy has the dimensions M L² T⁻², which ½mv² gives—M from m and L² T⁻² from v².
Correct answer: (A) Trigonal bipyramidal
In PCl₅ phosphorus is sp³d hybridized, so the molecule is trigonal bipyramidal.
Correct answer: (B) ClF₃
ClF₃ has three bond pairs and two lone pairs, which makes it T-shaped.
Correct answer: (C) C₂H₂
CO₂ is linear and so is C₂H₂, so the two are isostructural.
Correct answer: (C) Methane
The molecules of methane are held together only by weak van der Waals forces, so in the solid state it forms a molecular solid. Silica is a covalent network solid and calcium fluoride an ionic one.
Correct answer: (C) CO₂
CO₂ is linear and symmetrical, so the dipoles of the two C=O bonds cancel and the net dipole moment is zero.
Correct answer: (A) 3
HC≡C–CH=CH–CH₃ has two π bonds in the triple bond and one in the double bond—three in all.
Correct answer: (B) Lone pair–lone pair
The order of repulsion is lone pair–lone pair > lone pair–bond pair > bond pair–bond pair, so it is greatest between two lone pairs.
Correct answer: (A) C₄H₁₀O
In C₄H₁₀O the oxygen of an ether can carry different alkyl groups on either side, so that is the molecule which shows metamerism.
Correct answer: (A) Is released and an ionic bond is formed
Sodium gives up an electron and chlorine takes it; energy is released in the process and an ionic bond is formed.
Correct answer: (B) Acetone
The highest vapour pressure means the lowest boiling point, and acetone's 12.36 kPa is the highest of the three.
Correct answer: (B) Less than the critical temperature
A gas can be liquefied by pressure alone only below its critical temperature; above it no pressure will liquefy it.
Correct answer: (A) 2NO₂(g) ⇌ 2N₂(g) + O₂(g)
In homogeneous equilibrium every species is in the same phase—2NO₂(g) ⇌ 2N₂(g) + O₂(g) is all gaseous, while the others involve a solid.
Correct answer: (A) Zero
On a hot metal surface the decomposition of ammonia becomes independent of concentration once the surface is saturated, so the reaction is of zero order.
Correct answer: (D) More than one of the above
The equilibrium constant serves both to predict the direction of the reaction and to calculate the concentrations at equilibrium, so the answer is ‘more than one’.
Correct answer: (B) nλ = 2d sin θ
Bragg's law is nλ = 2d sin θ, where d is the spacing between the planes of the crystal.
Correct answer: (A) NH₃, NH₄⁺, HCOOH
A conjugate acid has one proton added—NH₂⁻ gives NH₃, NH₃ gives NH₄⁺ and HCOO⁻ gives HCOOH.
Correct answer: (A) +7, +6, +7
Manganese in KMnO₄ is +7, chromium in K₂Cr₂O₇ is +6 and chlorine in KClO₄ is +7.
Correct answer: (B) ΔG = ΔH − TΔS
The Gibbs free energy equation is ΔG = ΔH − TΔS; a negative ΔG means the reaction is spontaneous.
Correct answer: (C) A proton is a Lewis base.
A proton accepts electrons, so it is a Lewis acid, not a base—that is the statement which is wrong.
Correct answer: (B) Increases
On evaporation the water molecules become far more disordered, so the entropy increases.
Correct answer: (B) 1.88
[H⁺] = 0.1 × 0.132 = 0.0132 mol per litre, so pH = −log(0.0132) ≈ 1.88.
Correct answer: (B) BaSO₄
BaSO₄ is insoluble in water, which is why it appears as a white precipitate in the test for sulphate.
Correct answer: (B) Methyl orange is red in the acidic region and yellow in the alkaline region.
Methyl orange is red in acidic medium and yellow in alkaline medium—that is the correct statement.
Correct answer: (B) H₂S
Water is held together by hydrogen bonding, which lifts its boiling point; H₂S has none and is lighter than H₂Se, so its boiling point is the lowest.
Correct answer: (B) Phenolphthalein
For a weak acid (HCOOH) against a strong base (NaOH) the equivalence point lies on the alkaline side, so phenolphthalein is the suitable indicator.
Correct answer: (E) None of the above
The strength of the halogen acids rises down the group—HF the weakest and HI the strongest. By the key no option states that order correctly, so the answer is ‘None of the above’.
Correct answer: (D) More than one of the above
A negative E° marks a strong reducing couple and a positive E° a weak one—both statements hold; oxidation, however, takes place at the anode. So the answer is ‘more than one’.
Correct answer: (C) sp³d
Chlorine in ClF₃ has five electron pairs about it, so the hybridization is sp³d.
Correct answer: (A) F⁻, HSO₄⁻, CO₃²⁻
A conjugate base has one proton removed—HF gives F⁻, H₂SO₄ gives HSO₄⁻ and HCO₃⁻ gives CO₃²⁻.
Correct answer: (B) 3s² 3p⁶ 3d⁵ 4s¹
Chromium is 3d⁵ 4s¹, because a half-filled d subshell gives extra stability.
Correct answer: (D) More than one of the above
Magnetic separation and froth flotation are both used to concentrate an ore; roasting comes after concentration. So the answer is ‘more than one’.
Correct answer: (A) +8
The highest oxidation state shown by a transition metal is +8, seen in osmium and ruthenium.
Correct answer: (A) Van Arkel method
Zirconium and titanium are purified by the van Arkel method, in which the iodide is formed and then decomposed on a hot filament.
Correct answer: (C) ΔG is negative
A cell reaction is spontaneous only when ΔG is negative, that is when the cell potential is positive.
Correct answer: (C) Methane
In methane every valence electron goes into bonding—no lone pair is left over and none is lacking, so it is the electron-precise hydride.
Correct answer: (A) 35
In [Cu(NH₃)₄]²⁺ the Cu²⁺ has 29 − 2 = 27 electrons and the four ligands give eight more, so the effective atomic number is 35.
Correct answer: (D) More than one of the above
Large ions such as potassium, rubidium and caesium form superoxides; lithium does not. So the answer is ‘more than one’.
Correct answer: (D) More than one of the above
Calcium and strontium impart colour to the flame, but magnesium's high ionization enthalpy keeps it from doing so. Hence ‘more than one’.
Correct answer: (A) Potassium hexacyanoferrate(III)
Iron in K₃[Fe(CN)₆] is in the +3 state, so the IUPAC name is potassium hexacyanoferrate(III).
Correct answer: (A) Gypsum
Adding gypsum slows the setting of cement, which leaves time to work with it.
Correct answer: (C) [Ni(CN)₄]²⁻
Nickel in [Ni(CN)₄]²⁻ is dsp² hybridized, which makes the complex square planar.
Correct answer: (C) Magnesium sulphate
Magnesium sulphate, Epsom salt, is given in medicine as a purgative.
Correct answer: (B) Na₂[Fe(CN)₅(NO)]
Sodium nitroprusside is Na₂[Fe(CN)₅(NO)], which gives the violet colour in the test for sulphide.
Correct answer: (C) Borazine
Borazine (B₃N₃H₆) is called ‘inorganic benzene’, its ring being hexagonal like benzene's.
Correct answer: (C) Free radical
In homolytic fission the two electrons of the bond are shared out equally, so free radicals are formed.
Correct answer: (B) LiBH₄
LiBH₄ is used as a reducing agent in organic synthesis, since it supplies the hydride ion.
Correct answer: (B) Br⁺
Br⁺ carries a positive charge and so seeks electrons—that is the electrophilic reagent. OH⁻ is a nucleophile.
Correct answer: (C) Silicon carbide
Silicon carbide (SiC) is known as carborundum and, being extremely hard, serves as an abrasive.
Correct answer: (C) Polarimeter
The rotation of plane-polarized light is measured with a polarimeter.