why must a clean rod be used each time?

Answer 1

Are you eating with it? building a fire with it? scratching your back with it? what?

Answer 2

no like when you use it in an experiment of a precipitate

Answer 3

You don't want to take the chance of contaminating the ppt. Frankly, I think it's ok to stir with a glass rod, rinse it thoroughly with water from a wash bottle, and reuse the same glass rod as long as it hasn't been in contact with any other surface (meaning that you hold the glass rod in your hand until ready to use it again AND you don't let the part of the glass rod that will be dipped into the solution or ppt touch anything.).

Answer 4

thanks alot!!

Answer 5

oh another question pliz... why different masses of ppt were obtained for test tube IV and V??... LAB QUESITONS

Answer 6

Aw C'mon. I'm not a mind reader. What ppt? What masses? What chemicals? What experiment? What's in test tube IV and V initially and what was added to each?