Question #2b76b

Equivalent weight definitions are dependent upon type of reation; That is, one for oxidation-reduction reactions and one for metathesis reactions.

For oxidation-reduction reactions , one equivalent weight is the mass of substance that will transfer 1 mole of electrons during the redox process.

Example: #Mg^o(s) + 2HCl(aq) => MgCl_2(aq) + H_2(g)#

#Mg^o(s)#=> #Mg^(+2)# + #2e^-#
For 1 equivalent wt of Mg(s) => #1/2Mg^o(s)#=> #1/2MgCl_2(aq) + e^-#

This says that #1/2"mole" Mg^o(s)# will deliver 1 #"mole"color(white)(m)e^-# => 1 equivalent wt of Mg is 1/2 mole weight of Mg or 1/2(24g/mole) = 12 grams Mg per eqv. wt.

From a reaction perspective:
1 eqv wt #Mg^o(s)# + 1 eqv wt #HCl# => 100% Theoretical Yield=> That is, 12 gms of #Mg^o# will react completely with 36 gms of #HCl#.

In Metathesis processes, one equivalent weight is the mass of substance that will deliver one mole of cationic charge or one mole of anionic charge in the the double replacement process. Such does not involve changes in oxidation states of the elements during this process.

Example:
#AgNO_3(aq) + NaCl(aq)# => #NaNO_3(aq) + AgCl(s)#

In this process 1 mole #AgNO_3# => one mole cation (#Ag^+#)
=> 1 eqv wt #AgNO_3# = 169 g/eqv. wt.

Also, in this process 1 mole of #NaCl(aq)# => one mole of anion (#Cl^-#) => 1 eqv wt #NaCl# = 58 g/eqv wt.

From a reaction perspective:
1 eqv wt #AgNO_3#(aq) + 1 eqv wt#NaCl# => 100% Theoretical Yield
=> That is, 169 gms of #AgNO_3# with react completely with 58 gms #NaCl#