What is the element oxidized and the element reduced in the equation:

Question

HAsO2 + 2 Ag+ + 2 H2O 2 Ag + H3AsO4 + 2 H+

Answer 1

Go through the equation and assign oxidation numbers to each element. Look at the elements that have changed oxidation state. The loss of electrons is oxidation and gain of electrons is reduction.
Here is how you assign oxidation numbers.
http://www.chemteam.info/Redox/Redox-Rules.html