Chemistry XII Unit 4 Questions: 50 Time Limit: 50 minutes Passing Score: 60% Start Quiz Chemistry XII Unit 4 Question 1 of 50 What is the general electronic configuration of d-block elements? (n-1)d¹⁻¹⁰ns¹⁻² (n-1)d¹⁻⁸ns² nd¹⁻¹⁰ns² (n-1)d¹⁻⁹ns¹⁻² Which of the following is NOT a property of transition metals? High tensile strength Metallic lustre Low melting points High electrical conductivity Why is Zn not considered a transition element? It has no d-electrons It has completely filled d-orbitals (3d¹⁰) in ground and oxidation states It cannot form colored compounds It is not paramagnetic What is the electronic configuration of Chromium (Z=24)? 3d⁴4s² 3d⁵4s¹ 3d⁶4s⁰ 3d³4s³ What is the electronic configuration of Copper (Z=29)? 3d⁹4s² 3d¹⁰4s¹ 3d⁸4s³ 3d¹⁰4s⁰ Which series belongs to the 3d transition elements? Sc to Zn Y to Cd La to Hg Ac to Cn Why do transition metals have high enthalpy of atomisation? They have large atomic size They involve greater number of electrons from (n-1)d and ns orbitals in metallic bonding They have low ionization energy They are soft metals At which electronic configuration is the enthalpy of atomisation maximum in a transition series? d³ d⁵ d⁷ d¹⁰ What is lanthanoid contraction? Increase in atomic size across lanthanoids Gradual decrease in atomic and ionic radii from La to Lu Increase in ionic charge Decrease in oxidation states Why does lanthanoid contraction occur? Due to increase in nuclear charge Due to imperfect shielding of one 4f electron by another Due to loss of electrons Due to increase in atomic mass What is the consequence of lanthanoid contraction on 5d elements? 5d elements are larger than 4d elements 5d and 4d elements have similar atomic radii 5d elements have lower density 5d elements are more reactive Which oxidation state is most common for transition metals? +1 +2 +3 +4 Which element exhibits maximum number of oxidation states in 3d series? Chromium Manganese Iron Cobalt Why do transition elements show variable oxidation states? Due to large atomic size Due to incompletely filled d-orbitals with similar energies Due to high electronegativity Due to metallic character Which ion has d⁵ electronic configuration? Fe²⁺ Mn²⁺ Cr³⁺ Ti²⁺ Why is Cr²⁺ a strong reducing agent? It oxidizes easily to Cr³⁺ (d³) which has stable half-filled t₂g level It has high ionization energy It is highly electronegative It has large atomic size Why is Mn³⁺ a strong oxidizing agent? It gains electrons easily It reduces easily to Mn²⁺ (d⁵) which has stable half-filled d-subshell It has low ionization energy It is highly electronegative Which of the following has highest standard electrode potential E⁰(M²⁺/M)? Cu²⁺/Cu Zn²⁺/Zn Fe²⁺/Fe Mn²⁺/Mn Why does Cu have positive E⁰(Cu²⁺/Cu) value? High enthalpy of atomisation and low hydration enthalpy Low ionization energy High electronegativity Large atomic size What is the formula of potassium dichromate? K₂CrO₄ K₂Cr₂O₇ KCrO₄ KMnO₄ What is the oxidation state of Cr in K₂Cr₂O₇? +4 +5 +6 +7 What is the structure of dichromate ion Cr₂O₇²⁻? Linear Two tetrahedra sharing one corner with Cr-O-Cr bond angle 126° Octahedral Planar How is K₂Cr₂O₇ prepared from chromite ore FeCr₂O₄? By fusion with Na₂CO₃ in air to give Na₂CrO₄, then acidification and treatment with KCl By direct heating with KCl By reduction with carbon By electrolysis What is the color of K₂Cr₂O₇ crystals? Yellow Orange Green Purple What is the balanced equation for chromate-dichromate interconversion in acidic medium? 2CrO₄²⁻ + 2H⁺ ⇌ Cr₂O₇²⁻ + H₂O CrO₄²⁻ + H⁺ ⇌ Cr₂O₇²⁻ Cr₂O₇²⁻ + H₂O ⇌ 2CrO₄²⁻ + 2H⁺ CrO₄²⁻ + 2H⁺ ⇌ H₂CrO₄ What is the reduction half-reaction of acidified dichromate? Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O Cr₂O₇²⁻ + 6e⁻ → 2Cr³⁺ Cr₂O₇²⁻ + 2H⁺ + 2e⁻ → 2CrO₄²⁻ + H₂O Cr³⁺ + 3e⁻ → Cr What does acidified K₂Cr₂O₇ oxidize Fe²⁺ to? Fe⁰ Fe³⁺ Fe⁴⁺ FeO What is the formula of potassium permanganate? KMnO₃ KMnO₄ K₂MnO₄ K₃MnO₄ What is the oxidation state of Mn in KMnO₄? +5 +6 +7 +4 What is the color of KMnO₄ crystals? Yellow Orange Dark purple (almost black) Green How is KMnO₄ prepared commercially? By fusion of MnO₂ with KOH and O₂ to give K₂MnO₄, then electrolytic oxidation By direct oxidation of Mn with KNO₃ By reduction of Mn₂O₇ By heating MnO₂ with KCl What is the structure of permanganate ion MnO₄⁻? Linear Tetrahedral Octahedral Square planar Is KMnO₄ paramagnetic or diamagnetic? Paramagnetic Diamagnetic Ferromagnetic Antiferromagnetic What is the reduction product of KMnO₄ in acidic medium? MnO₄²⁻ MnO₂ Mn²⁺ Mn⁰ What is the reduction product of KMnO₄ in neutral or alkaline medium? Mn²⁺ MnO₂ Mn⁰ MnO₄²⁻ What does acidified KMnO₄ oxidize oxalic acid to? CO CO₂ HCOOH C What does acidified KMnO₄ oxidize H₂S to? SO₂ SO₄²⁻ S (sulphur) H₂SO₃ Which lanthanoid element can exhibit +4 oxidation state? La Ce Eu Yb What is the most common oxidation state of lanthanoids? +2 +3 +4 +5 What is the general electronic configuration of lanthanoids? [Xe]4f¹⁻¹⁴5d⁰⁻¹6s² [Xe]4f⁰⁻¹⁴5d¹6s² [Kr]4f¹⁻¹⁴6s² [Rn]5f¹⁻¹⁴6d⁰⁻¹7s² Which lanthanoid ion can act as a reducing agent? Ce⁴⁺ Eu²⁺ Gd³⁺ Lu³⁺ Why are lanthanoid ions colored? Due to s-electrons Due to f-f transitions Due to d-d transitions Due to metallic bonding What is the electronic configuration of Ce⁴⁺? [Xe]4f¹ [Xe]4f⁰ [Xe]4f² [Kr]4f⁰ What is actinoid contraction? Increase in atomic size across actinoids Gradual decrease in atomic and ionic radii from Ac to Lr Increase in ionic charge Decrease in oxidation states What is the general electronic configuration of actinoids? [Xe]4f¹⁻¹⁴5d⁰⁻¹6s² [Rn]5f¹⁻¹⁴6d⁰⁻¹7s² [Rn]6d¹⁻¹⁰7s² [Kr]4f¹⁻¹⁴6s² Which actinoid elements are radioactive? Only first few Only last few All actinoids None Why is actinoid chemistry more complex than lanthanoid chemistry? Actinoids are more reactive Actinoids exhibit wider range of oxidation states Actinoids have larger atomic size Actinoids are non-metals What is the use of misch metal alloy containing lanthanoids? In catalysts In making bullets, shells and lighter flints In batteries In pigments Which oxide is used as catalyst in Contact Process for H₂SO₄ manufacture? Fe₂O₃ V₂O₅ MnO₂ Cr₂O₃ Which metal catalyst is used in Haber process for NH₃ synthesis? Nickel Platinum Iron Copper Previous Next Submit Quiz Want to save your progress? Create an account or log in to track your quiz scores! Register/Login