The increasing order of acidity of pentafluorides (SbF5, NbF5, PF5, AsF5 and TaF5) in fluorosulphonic acid is :
SbF5 > AsF5 > TaF5 > NbF5 > PF5
In fluorosulphonic acid, HSO3F, a pentafluoride acts as a Lewis acid by accepting a fluoride (or fluorosulfate) ion, which shifts the self-ionisation and raises the concentration of the protonated solvent H2SO3F+: \(2HSO_{3}F + MF_{5} \rightleftharpoons H_{2}SO_{3}F^{+} + [MF_{5}(SO_{3}F)]^{-}\).
The stronger the fluoride-ion acceptor (Lewis acid), the more stable its anion and the larger the increase in acidity. Conductivity and Hammett acidity measurements (Gillespie) give the acid-enhancing order SbF5 > AsF5 > TaF5 > NbF5 > PF5.
SbF5 is the strongest known fluoride acceptor (it forms "magic acid" with HSO3F); AsF5 is somewhat weaker; the heavier group 5 fluorides TaF5 and NbF5 are moderate acceptors, with TaF5 the stronger; and PF5, with a small central atom, is the weakest acceptor in the series.
Orders placing PF5 above TaF5 and NbF5, treating TaF5 and NbF5 as equal, or reversing the whole series do not agree with these measurements.
Therefore the acidity order is SbF5 > AsF5 > TaF5 > NbF5 > PF5.
Hence, SbF5 > AsF5 > TaF5 > NbF5 > PF5.
Important Questions from Mixed Topic (MH-SET)
.................... is a client server application that identifies each host on the internet with a unique user-friendly name.
Every OS has a ................ or .......... which primarily resides in the main memory of the computer to perform some of the basic functions of the OS.
(i) Kernel
(ii) Interface
(iii) Nucleus
(iv) Compiler
Codes:
Which of the following are referred to as low level language?
(i) Machine language
(ii) Assembly language
(iii) High level language
(iv) Natural language
Codes:
Match the following:
List I List II (a) New York Public Library (i) Shelv AR (b) Miami University Augmented Research Group (ii) Smart library (c) Oula University Library (iii) Wolf Walk (d) North Carolina State University (iv) Find the future Codes:
Which part of the QR code represents the encoded data?
