Astudent dissolves 0.2975 g of the unknown weak acid to give 100. ml solution. s/he obtains the following titration curve for his/her best titration. at the equivalence point, 19.0 ml of 0.1000 m naoh was added.(a) calculate the molar mass of the acid. g/mol(b) what is the pka of the acid?

MM = 156.57 g/mol

pH at V = 9.5 mL will be the pKa value for the acid

Explanation:

solution

for the molar mass  MM is here express as

MM =   .....................1

here  

mass = 0.2975  g

and

mol = MV = 0.1000 × 19 ×

MV = 0.0019 mol of acid

so

MM =  

MM = 156.57 g/mol

and

we know for pKa the easiest way is to find the half equivalence point  is

V half = 0.5 × Vtitration

V half =  0.5 × 19

V half  = 9.5 mL

so  pH at V = 9.5 mL will be the pKa value for the acid

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-