chemistry- word problem

Question

A solution is to be standardized by titration KMnO4(aq) against As2O3(s). A 0.1072-g sample of As2O3 requires 24.35 mL of the KMnO4(aq) for its titration.
5As2O3+4MnO^-4+9H2O+12H+→10H3AsO4+4Mn2+. 

Part A

What is the molarity of the KMnO4(aq)?

Express your answer using four significant figures.

Answer 1

Molarity=moles/volume

 

Moles KMnO4=moles As2O3*(4 moles MnO4-/5 moles As2O3)

 

Moles As2O3=0.1072/197.8414

Divide given mass by molar mass.

 

Moles As2O3=0.0005418 moles

 

Moles MnO4-=0.0005418*(4/5)

 

Moles MnO4-=0.0004335

 

Molarity KMnO4=0.0004335 moles/0.02435 L or 0.01780 M