What are the different oxidation states exhibited by the lanthanoids?
Lanthanides exhibits + 2, + 3 and + 4 oxidation states. The most corrtmon oxidation state of lanthanoids is +3.
Assertion (A): Cu can not libirate hydrogen from acids .
Reason (R): because it has positive electrode potential.
Actinoid contraction is greater from element to element than lanthanoid contraction. Why?
What may be the stable oxidation state of the transition element with the following delectron configurations in the ground state of their atoms: 3d3,3d5, 3d8 and 3d4?
Although fluorine is more electronegative than oxygen, but the ability of oxygen to stabilize higher oxidation states exceeds that of fluorine. Why?
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct answer out of the following choices:
(a) Both Assertion and Reason are true and the Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true and the Reason is not the correct explanation of Assertion.
(c) Assertion is not true but the Reason is true.
(d) Both Assertion and Reason are false.
Assertion (A): Cu2+ iodide is not known.
Reason (R): Cu2+ oxidises I to iodine.
When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallized from the solution. When compound (C) is treated with KCl, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.
While filling up of electrons in the atomic orbitals, the 4s orbital is filled before the 3d-orbital but reverse happens during the ionization of the atom. Explain why?
When a brown compound of manganese
(A) is treated with HCl, it gives a gas
(B) The gas taken in excess, reacts with NH3 to give an explosive compound
(C) Identify compounds A, B and C.
Although Cr3+ and CO2+ ions have same number of unpaired electrons but the magnetic moment of Cr3+ is 3.87 BM and that of CO2+ is 4.87 BM. Why?
Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them. Why?
Assertion (A): The highest oxidation state of osmium is +8.
Reason (R): Osmium is a 5d-block element.
Which is the last element in the series of the actinoids? Write the electronic configuration of this element. Comment on the possible oxidation state of this element
Gadolinium belongs to 4f series. Its atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?
Explain why does colour of KMnO4 disappear when oxalic acid is added to its solution in acidic medium?
Explain giving reasons:
(i)Transition metals and many of their compounds show paramagnetic behaviour.
(ii)The enthalpies of atomisation of the transition metals are high.
(iii)The transition metals generally form coloured compounds.
(iv)Transition metals and their many compounds act as good catalyst
For M2+/M and M3+/M2+ systems the E ° values for some metals are as follows:
Cr2+/Cr –> -0.9 V
Mn2+/Mn –> -1.2V
Fe2+/Fe –> -0.4 V
Cr3+/Cr2+ –> -0.4 V
Mn3+/Mn2+ –>+ 1.5V
Fe3+/Fe2+ –>+ 0.8V
(ii) the ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.
Compare the chemistry of actinoids with that of lanthanoids with reference to:
(i) Electronic configuration
(ii) Oxidation states
(iii) Chemical reactivity
Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements.
KMnO4 acts as an oxidizing agent in acidic medium. The number of moles of KMn04 that will be needed to react with one mole of sulphide ions in acidic solution is
Generally, transition-elements and their salts are coloured due to the presence of unpaired electrons in metal ions. Which of the following compounds are coloured?
(a) kMnO4 (b) Ce(SO4)2 (c) TiCl4 (d) Cu2Cl2
Although +3 is the characteristic oxidation state for lanthanoids but cerium
also shows +4 oxidation state because
(a) it has variable ionization enthalpy
(b) it has a tendency to attain noble gas configuration
(c) it has a tendency to attain f ° configuration
(d) it resembles Pb4+
A violet compound of manganese (A) decomposes on heating to liberate oxygen and compounds (B) and (C) of manganese are formed. Compound (C) reacts with KOH in the presence of potassium nitrate to give compound (B). On heating compound (C) with cone. H2SO4 and NaCl, chlorine gas is liberated and a compound (D) of manganese along with other products is formed. Identify compounds A to D and also explain the reactions involved.
Silver atom has completely filled d orbitals (4d10) in its ground state. How can you say that it is a transition element?
A solution of KMnO4 on reduction yields either a colourless solution or a brown precipitate or a green solution depending on pH of the solution. What different stages of the reduction do these represent and how are they carried out?
Mention the type of compounds formed when small atoms like H, C and N get trapped inside the crystal lattice of transition metals. Also give physical and chemical characteristics of these compounds.
(a) Transition metals can act as catalysts because these can change their oxidation state.
How does Fe(III) catalyse the reaction between iodide and persulphate ions?
(b) Mention any three processes where transition metals act as catalysts.
Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?
Calculate the number of unpaired electrons in the following gaseous ions : Mn3+, Cr3+, V3+ and Ti3+. Which one of these is the most stable in aqueous solution.
Indicate the steps in the preparation of:
(i) K2Cr207from chromite ore
(ii) KMn04 from pyrolusite ore.
When KMnO4 solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because
(a) CO2 is formed as the product (b) Reaction is exothermic
(c) Mn04 catalyses the reaction (d) Mn2+ acts as autocatalyst
In the form of dichromate, Cr (VI) is a strong oxidizing agent in acidic medium but Mo (VI) in MoO3 and W (VI) in WO3 are not because
(a) Cr (VI) is more stable than Mo(VI) and W(VI)
(b) Mo(VI) and W(VI) are more stable than Cr(VI)
(c) higher oxidation states of heavier members of group-6 of transition series are more stable
(d) lower oxidation states of heavier members of group-6 of transition series are more stable
Transition elements form binary compounds with halogens. Which of the following elements will form MF3 type compounds?
(a) Cr (b) Co (c) Cu (d) Ni
When orange solution containing Cr2O72- ion is treated with an alkali, a yellow solution is formed and when H+ ions are added to yellow solution, an orange solution is obtained. Explain why does this happen?
Assertion (A): The highest oxidation state of osmium is +8.
Reason (R): Osmium is a 5d-block element.
Write down the electronic configuration of (i) Cr3+ (ii) Pm3+ (iii) Cu+ (iv) Ce4+(v) Co2+ (vi) Lu2+(vii) Mn2+ (viii) Th4+.
Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.
Compare the stability of +2 oxidation state for the elements of the first transition series.
Calculate the number of unpaired electrons in the following gaseous ions : Mn3+, Cr3+, V3+ and Ti3+. Which one of these is the most stable in aqueous solution.
Give examples and suggest reasons for the following features of the transition metal chemistry:
(i) The lowest oxide of transition metal is basic the highest is amphoteric/ acidic.
(ii) A transition metal exhibits highest oxidation state ih oxides and fluorides.
(iii) The highest oxidation state is exhibited in oxoanions of a metal.
Which of the following actinoids show oxidation states up to +7?
(a) Am (b) Pu (c) U (d) Np
