What are the three main groups of elements? * metals, noble gases, and metalloids

metals, non-metals, and metalloids

metals, liquids, and gases

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

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.