The electron dot structure (Lewis structure) for which of the following molecules would have two unshared pairs of electrons on the central atom? A) H2S
B) NH3
C) CH4
D)HCN
E) CO2

Which of the following is true for the actual yield of a reaction? it is always calculated as a ratio. it is the yield from the excess reactant. it is the yield from the limiting reactant. it is always less than the theoretical yield.

The excretory system, need answers for all: )

A4.86 g piece of metal was placed in a graduated cylinder containing 15.5 ml of water. the water level rose to 17.3 ml. what is the density of the metal. i need the steps of how to solve it to so i can use a formula to work out other problems.