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प्रश्न
What are interstitial compounds?
What are interstitial compounds? Why do these compounds have higher melting points than corresponding pure metals?
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उत्तर
- Interstitial compounds are those which are formed when small atoms like H, C, N, B, etc. are trapped inside the crystal lattice of metals.
- They have a higher melting point than metals because the metal-nonmetal bonds are stronger than the metal-metal bonds in pure metals.
- They are usually non-stoichiometric and are neither typically ionic nor covalent; for example, TiC, Mn4N, Fe3H, VH0.56, and TiH1.7.
संबंधित प्रश्न
Why is Sc3+ colourless while Ti3+ coloured? (Atomic number Sc = 21, Ti =22)
How would you account for the following?
Transition metals exhibit variable oxidation states.
The elements of 3d transition series are given as: Sc Ti V Cr Mn Fe Co
Answer the following: Write the element which shows maximum number of oxidation states. Give reason.
Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?
Why are Mn2+ compounds more stable than Fe2+ towards oxidation to their +3 state?
Which of the d-block elements may not be regarded as the transition elements?
For M2+/M and M3+/M2+ systems, the E° values for some metals are as follows:
| Cr2+/Cr | −0.9 V |
| Mn2+/Mn | −1.2 V |
| Fe2+/Fe | −0.4 V |
| Cr3/Cr2+ | −0.4 V |
| Mn3+/Mn2+ | +1.5 V |
| Fe3+/Fe2+ | +0.8 V |
Use this data to comment upon:
- The stability of Fe3+ in acid solution as compared to that of Cr3+ or Mn3+ and
- the ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.
Write down the number of 3d electrons in the following ion:
Cu2+
Indicate how would you expect the five 3d orbitals to be occupied for this hydrated ions (octahedral).
Which one of the following ions is coloured?
How would you account for the following?
Transition metals and their compounds act as catalysts.
Give reasons Iron has the higher enthalpy of atomization than that of copper.
Why do transition elements show variable oxidation states ? In 3d series (Sc to Zn), which elements shows the maximum number of oxidation state and why ?
How is potassium dichromate prepared from chrome iron ore?
Account for the following :
Ti4+ is colourless whereas V4+ is coloured in an aqueous solutions.
Explain why Zn2+ salts are white whereas Cu2+ salts are coloured.
Give reason for the following:
The transition metals generally form coloured compounds.
Maximum oxidation state is shown by ____________.
Transition elements form binary compounds with halogens. Which of the following elements will form \[\ce{MF3}\] type compounds?
(i) \[\ce{Cr}\]
(ii) \[\ce{Co}\]
(iii) \[\ce{Cu}\]
(iv) \[\ce{Ni}\]
Which of the following will not act as oxidising agents?
(i) \[\ce{CrO3}\]
(ii) \[\ce{MoO3}\]
(iii) \[\ce{WO3}\]
(iv) \[\ce{CrO^{2-}4}\]
Why does copper not replace hydrogen from acids?
When a brown compound of manganese (A) is treated with \[\ce{HCl}\] it gives a gas (B). The gas taken in excess, reacts with \[\ce{NH3}\] to give an explosive compound (C). Identify compounds A, B and C.
Reactivity of transition elements decreases almost regularly from Sc to Cu. Explain.
Match the solutions given in Column I and the colours given in Column II.
| Column I (Aqueous solution of salt) |
Column II (Colour) |
| (i) \[\ce{FeSO2.7H2O}\] | (a) Green |
| (ii) \[\ce{NiCl2.4H2O}\] | (b) Light pink |
| (iii) \[\ce{MnCl2.4H2O}\] | (c) Blue |
| (iv) \[\ce{CoC12,6H2O}\] | (d) Pale green |
| (v) \[\ce{Cu2 Cl2}\] | (e) Pink |
| (f) Colourless |
Assertion: Separation of \[\ce{Zr}\] and \[\ce{Hf}\] is difficult.
Reason: Because \[\ce{Zr}\] and \[\ce{Hf}\] lie in the same group of the periodic table.
Identify A to E and also explain the reactions involved.
When an oxide of manganese (A) is fused with KOH in the presence of an oxidising agent and dissolved in water, it gives a dark green solution of compound (B). Compound (B) disproportionates in neutral or acidic solution to give purple compound (C). An alkaline solution of compound (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.
Identify the metal and justify your answer.
\[\ce{MO3F}\]
On the basis of the figure given below, answer the following questions:
- Why Manganese has lower melting point than Chromium?
- Why do transition metals of 3d series have lower melting points as compared to 4d series?
- In the third transition series, identify and name the metal with the highest melting point.
Which of the following maxm magnetic moment?
Which of the following species has maximum magnetic momentum?
A complex in which dsp2 hybridisation takes place is ______.
Why are all copper halides known except that copper iodide?
Which one among the following metals of the 3d series has the lowest melting point?
Assertion (A): Transition metals show their highest oxidation state with oxygen.
Reason (R): The ability of oxygen to form multiple bonds to metals.
Account for the following:
Copper has an exceptionally positive `"E"_("M"^(2+)//"M")^0` value.
Account for the following:
Eu2+ with electronic configuration [Xe]4f76s2 is a strong reducing agent.
The second ionization enthalpies of chromium and manganese are 1592 and 1509 kJ/mol respectively. Explain the lower value of Mn.
What is the oxidation state of chromium in chromate ion and dichromate ion?
Give a reason for the following.
Some transition metals and their compounds get attracted towards the magnetic field.
Why are interstitial compounds well known for transition metals?
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with iron (II) solution.
