Explain why it is best not to pipe ya liquid directly from a reagant bottle

Possibility of contamination

Explanation:

Taking a sample with a pipette from a reagent bottle directly might contaminate the entire solution. For example, if a pipette is not clean enough, any salt present will therefore dissolve in the given solution and change its purity. In worse cases, that salt might also react with the given solution and produce new products.

Another example is when a clean pipette is used but isn't dry. The resultant water will essentially dilute the solution and will change its molarity. If that solution needs to have an exact standardized molarity, the reading will then not correspond to its actual concentration and such a solution couldn't be used for a titration and would have to be standardized.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.