Reactant A diffuses and reacts within a spherical, porous catalyst. The reaction is first-order and irreversible. At zero time, the catalyst, which contains no A, is dropped into a liquid bath containing a constant concentration of A. Use a shell balance to derive the governing partial differential for the concentration c(r, t) of A within the catalyst. Also, specify the initial and boundary conditions, assuming that the mass-transfer Biot number1 is infinite

where is the following

explanation:

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answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.