Question in my prelab: Why is nitric acid added dropwise?

Question

aaronq · Answer

you have to provide some context. Acid may be a catalyst in the reaction. 
what is the lab about?

abb0t · Answer

titration lab?

anonymous · Answer

it is the "A chemical reaction between tin and nitric acid" lab

abb0t · Answer

Well, your reaction is as follows: $\sf \color{red}{Sn + 2~HNO_3 \rightarrow Sn(NO_3)_2 + H_2}$

anonymous · Answer

ok, great! In the procedure part of the lab it says to add the nitric like this: "place the crucible on wire gauge in the hood and carefully add 10 M nitric acid dropwise evenly over the surface of the tin, no faster than one drop per second, until the reaction seems complete (about 100 drops). "

anonymous · Answer

Im not exactly sure of the professor is trying to ask me here, the question is pretty vague.

anonymous · Answer

any ideas? @abb0t

abb0t · Answer

Add the nitric acid dropwise. lol. I don't see what is unclear about that.

anonymous · Answer

haha exactly but the prelab is asking me why..