I need help with 5 question

I’m studying for my Chemistry class and need an explanation.

1-Describe how to safely smell a substance.

2- Give two reasons why it is important to separate waste for disposal.

3- Give two reasons why eating and drinking are not allowed in the laboratory.

4- What do we do with unused portions of chemicals?

5- Using the Internet, look of the SDS for silver nitrate. Write the LD50 for this substance.