A25.5 ml aliquot of hcl of unknown concentration was titrared with .113 m naoh. it took 51.2 ml of the base to reach the endpoint of the titration. the concentration (m) of the acid was ?

0.227 M

Volume of HCl = 25.5 mL or 25.5 / 1000 => 0.0255 L

Molarity or concentration of NaOH  = 0.113 M

Volume of NaOH  = 51.2 mL / 1000 = 0.0512 L

Number of moles NaOH:

Moles = Molarity x Volume

            = 0.113 x  0.0512

            = 0.0057856 moles of NaOH

From the equation we can obtain the mole ratio:

HCl + NaOH = NaCl + H2O

1 mole HCl : 1 mole NaOH

Therefore;

Moles of  HCl : 0.0057856 moles NaOH

Hence; moles of HCl  =  0.0057856 x 1 / 1

                                    =  0.0057856 moles of HCl

Molarity of  HCl = moles of HCL / Volume of HCl

                         M =  0.0057856 / 0.0255

                              = 0.227 M

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."