What is the charge of CO3?

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

The excretory system,need answers for all: )

Sodium nitrite (nano2) reacted with 2−iodooctane to give a mixture of two constitutionally isomeric compounds of molecular formula c8h17no2 in a combined yield of 88%. draw reasonable structures for these two isomers. click the "draw structure" button to launch the drawing utility. place the two compounds in the appropriate boxes below.