Copper becomes green when exposed to moist air for a long period. This is due to

  • A
    the formation of a layer of cupric oxide on the surface of copper.
  • B
    the formation of a layer of basic carbonate of copper on the surface of copper.
  • C
    the formation of a layer of cupric hydroxide on the surface of copper.
  • D
    the formation of basic copper sulphate layer on the surface of the metal.

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Consider three metal chlorides $x$,$y$ and $z$,where $x$ is water soluble at room temperature,$y$ is sparingly soluble in water at room temperature and $z$ is soluble in hot water. $x$,$y$ and $z$ are respectively:

Present a comparative account of the alkali and alkaline earth metals with respect to the following characteristics :
$(a)$ Tendency to form ionic/covalent compounds.
$(b)$ Nature of oxides and their solubility in water.
$(c)$ Formation of oxosalts.
$(d)$ Solubility of oxosalts.
$(e)$ Thermal stability of oxosalts.

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The correct solubility order is/are:
$I. CaCO_3 > SrCO_3 > BaCO_3$
$II. Li_2CO_3 < Na_2CO_3 < K_2CO_3$
$III. K_2CO_3 < Rb_2CO_3 < Cs_2CO_3$
$IV. Na_2CO_3 > K_2CO_3 > Rb_2CO_3$

Which of the following statements is not correct?

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Select the incorrect order for the given properties:
$(a)$ $A_2B < AB < A_2B_3 = \text{Lattice Energy (L.E.)}$ (Charge of $B = -2$)
$(b)$ $Na_2CO_3 < K_2CO_3 < Rb_2CO_3 < Cs_2CO_3 = \text{Thermal stability}$
$(c)$ $MgF_2 < CaF_2 < SrF_2 < BaF_2 < BeF_2 = \text{Solubility}$
$(d)$ $LiOH < NaOH < KOH < RbOH < CsOH = \text{Solubility and stability}$

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