38 . C
There are 6.023 × 10^23 atoms in a mole of a compound, so 1.204 × 10^24 atoms would be
approximately 2 moles of Br. 2 moles of Br × 80 g/mole = 160 g.39 . E
40 . E
γ decay is a high-energy emission that has no mass or charge. Therefore after γ decay
would still be .41 . C
The number of moles of solute in the solution will be the same after dilution as before, and the
number of moles in each case is equal to the molar concentration multiplied by the volume of
solution. This means that the initial concentration times the initial volume will be equal to the
final concentration times the final volume (M 1 V 1 = M 2 V 2 ). So, the final volume will equal
M 1 (V 1 )/M 2 . Plugging into this equation, we find that V 2 = 200 mL (50 mL + 150 ml).
42 . C
All members of Group IA have similar reactivities because they have a similar valence shell
configuration (one loosely bound electron). They lose it easily to form univalent cations and
react readily with nonmetals, especially halogens.
43 . E
One mole of a gas at STP will have a volume of 22.4 L. If the pressure is doubled, the volume
will halve since they are inversely proportional. If the temperature is tripled, the volume will
triple since they are proportional. 3/2(22.4 L) = 33.6 L.
44 . A