A solution of KNO3 consists of ions of potassium and nitrate. The ionic equation is expressed as:
KNO3 = K+ + NO3-
There is 1 is to 1 ratio between the substances. So, the molarity of NO3- in the solution is calculated as follows:
0.160 mol / L KNO3 ( 1 mol NO3- / 1 mol KNO3 ) = 0.160 M NO3-