i need a solution please help...chemistry?

Question

A KMnO4(aq) solution is to be standardized against As2O3(s) . A 0.1078g sample of As2O3 requires 22.15 ml of the KMnO4 (aq) for its titration . what is the molarity of the KMnO4(aq)?

5 AS2O3 + 4 MnO4 + 9 H2O + 12H ----> 10 H3AsO4 + 4 Mn

Answer 1

5As2O3 + 4MnO4- + 9H2O + 12H+ ==> 10H3AsO4 + 4Mn(2+)
5 moles As2O3 reacts with 4 moles of KMnO4.
Please, please adopt a good habit: (1) do not write As as AS; and (2) do not omit charge of ions.
Molar mass of As2O3: 197.841 g/mol
0.1078g As2O3 == 0.0005449 mole As2O3.
Thus the molarity of the KMnO4(aq) is:
0.0005449*(4/5)/0.02215 = 0.01968 (M)