12th Class Chemistry Chapter 6 Transition Elements Short Question Answers

Chemistry short QA

12th Class Chemistry Chapter 6 Transition Elements Short Question Answers Below

1.What are the d-block elements?why are they called so?
Those elements of periodic table whose outermost sub-shell is d-and it is in the process of completion are called d-block elements.There are four series of d-block elements i.e.3d,4d,5d and 6d in period number 4,5,6, and 7 respectively.
2.What are f-block elements?Why are they called so?
Those elements of the periodic table whose outermost sub-shell is f-and that is in the process of completion are called f-block elements.There are two series of f-block elements i.e.4f and 5f.They lie in sixth and seventh periods of the periodic table.
3.Why d-and f-block elements are called transition elements?
In the Periodic Table.d-and f-block elements lie in between s and p-black elements.So their properties lie in between s and p.That is why they are called transition elements.
4.Why the electronic distribution of chromium and copper are different from the rest of the elements of 3d series?
In case of 24Cr 3d-sub shell has four electrons normally.It promotes one electron from 4s-orbital and makes five electrons in 3d to make it half filled and get extra stability.Similarly copper promotes  one electron  from 4s-orbital to 3d to make it fulfilled and make it stable.
24Cr =…………….3d54s1
29Cu =……………3d104s-1
5.What are typical and non-typical transition elements and why are they called so?
The elements of group II-B and III-B are non-typical transition elements.They are at the boundaries of the series and their properties are not exactly identical to other d-block elements.The other d-block elements are typical transition elements.
6.How do you distinguish between outer transition and inner transition elements?
The transition elements of d-series are outer transition elements.There are four series of this category.The elements of f-block i.e. lanthanides and actinides are inner transition elements.
7.What is lanthanide contraction?
No doubt there is a increasing number of electrons from one d-series to the next but the excessive increase of nuclear charge does not allow the sizes of the elements to increase that much.This is called lanthanide contraction.
8.How the atomic radii of d-block elements vary from left to the right in period?
The atomic radii decrease from left to the right in all d-series.This is due to the increasing nuclear charges and same shielding effects.Anyhow Zn,Cd and Hg show the abnormal behavior due to their completely filled sub-shells.
9.How the ionization energy values change form left to the right in d-block elements?
Due to decreasing sizes from left to the right the ionization energy values should increase from left to the right but some of the elements like Cr and Ni in 3d-series show the abnormal behavior.
10.Justify the variation of binding energies in d-block elements from left to right?
The binding energies depend upon the number of unpaired electrons in the outermost sub-shell.They are maximum in the middle of the series.So binding energies increase from left to right up to the middle and then they decrease.
11.Why the melting and boiling points are maximum somewhere in the middle of the series of d-block elements?
The melting and boiling points depend upon the binding energies which are the results of number of unpaired electrons.Since the number of unpaired electrons in the middle of the d-block series are greater so melting and boiling points in the middle are greater.
12.What is paramagnetism?What are its units?
Those substances which when placed between magnetic poles allow the magnetic lines of forces pass through them are called paramagnetic.It is measured in Bohr magnaton(B.M).It is measured by Gouy’s balance.
13.How the property of paramagnetism is developed in the substances?
The unpaired electrons in the outermost orbitals of substances create the magnetic moment.This is due to the orbital motion and spin motion.This magnetic moment is influenced by the external magnetic field.
14.Why the maximum paramagnetic strength is associated with the middle elements of d-block series?
The elements in the middle of the series have greater number of unpaired electrons in their outermost orbitals.This will create greater values of magnetic moments.Hence they show greater paramagnetic strength.
15.What is the reason for the variations of oxidation states of transition elements?
This is due to the greater number of unpaired electrons in the outermost orbitals.These electrons can change the orbital due to small energy differences and so the oxidation states can vary.
16.What is the reason for the development of the colors in the compounds of transition elements?or What is d-d transition?
Colors are developed  due to the  jumping of electrons from low energy levels to the higher ones and vice versa.d-orbitals are split up  into t2g and orbitals.Electrons are promoted from  lower d-orbitals to higher d-orbitals and photons of light are absorbed.The color of the rest of the compounds depends upon the complementary color  which is absorbed.This is called d-d transition.
17.What are complementary colures?Give example?
When a particular wavelength is absorbed by a certain substance from the white light the rest of the light has a different colour from that one which is absorbed.SO that colour is called the complementary colour of the absorbed one.
18.Why the catalytic properties are associated with the transition elements?
The substances having unpaired electrons mostly act as catalysts.Actually they give the electrons to other species and make them activated and increase the rates of reactions.
19.What are interstitial compounds?
Those compounds in which the interstices of the transition metals in their crystal structures are filled by small sized atoms like H,C,B etc.are called interstitial compounds.
20.Give examples of alloys and give their properties?
Alloys are mixtures of two or more than two metals.For example brass bronze and coinage alloys are the best alloys.They are usually harder than pure metals.They have high melting points and more resistant to corrosion.
21.How many types of various parts are present in the transition metal complex?
Transition metal complexes consist of cations and anions with a few exceptions.One of the ion is complex which has central transition metal atom or ion and a few ligands are attached with that.
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K4[Fe(CN)6] gives 4K+ and [Fe(CN)6]-4
[Cu(NH3)4] SO4.give [Cu(NH3)4]+2 and SO-24.
23.What is co-ordinatin number and co-ordination sphere of a complex compounds?
The number of ligands which surround the central metal atom or ion is called co-ordination number.The collection of central metal atom with all the ligands is called co-ordination sphere.In [Cu(NH3)4] SO4 the C.N of Cu is 4 the molecules/atoms written in big brackets is co-ordination sphere.
24.What are chelates?
When a polydentate liganed surrounds the central metal atom or ion,cyclic co-ordination complex ions are produced.These are called chelates.
25. While naming the complex compounds how do you end with negatively charged ligands positively charged ligands and neutral ligands?
Negatively charged ligands end in O positively charged ligands end in ium and neutral ligands are called as such.
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i)Potassium hexachloroplatinate. Ii) Sodium pentacarbonyI managanese.iii)Dichlorobisethlene diamine cobalt iv) chloride potasium tetracyano cuprate. V) Pentacarbonyl iron.
27.Indicate the shapes of the transition metal ions in which the central metal atom or iron has sp3 dsp2 and dsp3 hybridization?
Fore sp3 hybridization the structure is tetrahedral.For dsp2 hybridization the structure is square planer.For dsp3 hybridization triangular bipyramid structure is produced.
28.Give the names and formulas for important ores of iron?
The important ores of iron are as follows:
Magnetite                            Fe3O4
Haematite                           Fe2O3
Limonite                               Fe2O3.3H2O.
Copper iron pyrite              CuFeS2.
29.How do you compare the cast iron wrought iron and steel with respect to the percentage of carbon?
Cast iron,                              carbon=2.5 -4.5%
Wrough iron                        carbon=0.1 -0.25%
Steel                                      carbon=0.25-2.5%
30.What are the uses of wrought iron?
It is extremely tough and used for the manufacture of those articles which have to stand serve and serve and sudden stresses.
31.How do you compare the wrought iron and steel with respect to carbon,sulphur manganese and phosphorus?
                                Wrought iron         Steel
%age of carbon                                0.12 – 0.25          0.1-1.5
%age of sulphur                               0.2 – 0.15            0.1 – 4.0
%age of manganese                        upto 0.25            0.02 – 0.2
%age of phosphorus                       0.04 – 0.2            0.04 – 0.07
32.How do you compare mild steel medium carbon steel and high carbon steel with respect to their carbon contents and their properties?
                                            %age of
Mild steel                                   0.1 – 0.2
Medium carbon steel               0.2 – 0.7
High carbon steel                      0.7 – 1.5
33.What is the role of acidic and basic lining in the open hearth process for the manufacture of steel?
Bisic lining of dolomite is a mixture of CaO and MgO.It removes the acidic impurity like sulphur and phosphorus.Acidic lining is of SO2 and it removes manganese and silicon.
34.Discuss the general shape of bessemer’s converter?
It is pear-shaped vessel made up of steel plates.There are holes at the bottom.It is held on a central axis and can be tilted.
35.How do you remove the entrapped gases from the steel?
A little aluminium or ferrosilicon is added .Aluminium combine with nitrogen to give aluminium nitride.Entrapped bubbles of gases are called blow holes.
36.How do compare the cast iron steel and wrought iron keeping in view their hardness malleability and melting points?
                 Cast iron                    Steel                                Wrought iron
carbon             2.5 – 4.5%                 0.25 – 2.5%                        0.12 – 0.25%
Hardness          hard                             medium                                  soft
Malleability     brittle                     malleable and brittle                malleable
37.Why the corrosion of metals is more rapid in the presence of water?
In the presence of water the layer of oxides sulphides or carbonates is dissolved in water.So the corrosion penetrates into the metal.
38.How does electrochemical theory explain the corrosion of aluminium in the presence of copper?
In the mixture of copper and aluminium,aluminium corrodes because it loses the electrons makes the AI+3 and give AI(OH)3.
39.How does the metallic coating prevent the corrosion?
When the surface of iron is covered with a layer of metal which is more active than iron, iron will be protected.For examples Zn,Sn,Al and Cr coatings can help to stop corrosion of iron.
40.Why does damaged tin plated iron get rusted quickly?
An electrochemical cell is set up where Sn loses electron and gives to Fe+2 , Fe+2  is oxidized and is prevented from rusting.
41.What are chromastes and dichromates?
Chromates are salt of H2CrO4 and dichromates are the salts of H2Cr2O7 and these are two acid of chromium.
42.How the acidic medium develops an equilibrium between chromate and dichromate ion?
When the medium is acidic then CrO4-2 ion changes to Cr2O7-2 ion and equilibrium lies in the favour of Cr2O7-2 .
43.Give the uses of potassium chromate and its structure?
K2CrO4 is used for the manufacture of pigments as a corrosion inhibitor  in dying and tanning of leather and as an indicator in AgNO3 titrations.The structure of K2CrO4 is that of CrO4-2 ion which is tetrahedral in shape.
44.How does K2Cr2O7. Act as an oxidizing agent in the presence of H2SO4?
K2Cr2O7.reacts with H2SO4 to give atomic oxygen which can oxidize other substances.
45.How the mixture of K2Cr2O7. And H2SO4 oxidizes H2S gas and FeSO4 separately?
The atomic oxygen released by acidified   K2Cr2O7 oxidizes H2S FeSO4 to Fe(SO4)3.
46.What is chromyl test?
When mixture of K2Cr2O7. And a solube chloride say NaCI is heated with conc. H2SO4 then a deep red coloured liquid appears in the form of fumes having the formula CrO2CI2.This is called chromyl chloride.
47.Give the uses of K2Cr2O7?
It is used for the dying of many substances and in leather industry for chrome tanning.It acts as an oxidizing agent.It is used in calcoprinting and used in volumetric analysis analysis of redox titration.
48.How do you compare KMnO4 and K2MnO4?
These two compounds differ from each other in the oxidation number of manganese which is +6 and +7 in K2MnO4 and KMnO4 respectively.
49.How KMnO4 and H2SO4 act as oxidizing agents?
They react with each other to release atomic oxygen which can oxidize other substances.
50.How KMnO4 can be prepared by electrolytic method?
By the electrolytic oxidation K2MnO4 we get KMnO4.When electrical current is passed water decomposes.Hydrogen is collected at the cathode and oxygen at the anode.The oxygen liberated at the anode oxidizes MnO-2 ion to MnO4-1 ion.The oxidization number of the manganese increases from +6 t0+7.

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