Sieve theory of semipermeable membrane

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Sieve theory: 

 In this theory semipermeable membrane is considered as a sieve consisting of large number of fine pores. These pores allow the molecules of solvent which are similar in size through them as compared to the size of solute molecules. But this theory fails explain the cases where solute molecules are smaller in size than solvent molecules.

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Siemens Ozoniser how Siemens Ozoniser work

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Siemens Ozoniser:  This Ozoniser consist of two co-axial glass tubes fused together at one end. The outer side of the outer glass tube and the inner side of the inner glass tube are finally coated with tin foils as shown in the figure given below.  (Siemens Ozoniser)->2                                                     (Siemens Ozoniser)->1 These tin foil are connected  to the induction coil for supply of silent electric discharge. Pure and dry oxygen gas is passed into the apparatus through annular space. The gas is then subjected to the action of silent electric discharge where oxygen gets converted into ozone. The ozonised oxygen then comes out  of the apparatus through the outlet of the Ozoniser. (Siemens Ozoniser)->2
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Rutile structure

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Rutile structure: The radius radio is in the range 0.73 to 0.41. in rutile (TiO²) each Ti⁴+ ion is octahedrally surrounded by six O²- ions whereas each other O²- ion is surrounded by only three Ti⁴+ ions arranged at the tree corners of a plane triangle. The Co-ordination number of Ti⁴+ and O²+ ions are 6 and 3, respectively. It is not exactly a close packed structure. Ti⁴+ ions in rutile may however, be considered as forming a sufficiently distorted body centred cubic lattice.           Example  compounds  having radius ratio below 0.41 are SiO² and BeF² but these are only a few. The Co-ordination number of Si⁴+ and Be²+ is four and that of O²- is two. However, these are appreciably co-valent.
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F - block element What are f - block elements

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What are F - Block Elements - F - block elements are consist of Lanthanides and Actinides. In Lanthanides, they are 14 element immediately following Lanthanum (57) from cerium (58) to lutecium (71) . These 14 element are called Lanthanides . These Lanthanides belong to first inner transition series .           In Actinides , these are also 14 elements immediately following Actinium (89) starting from Thorium (90) to lawrencium (103) . The element from Th (90) to Lr (103) are called Actinides . They belong to second inner transition series.
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