Answers and Explanations

PRACTICE TEST 3

1. Part A

1 . A

Molecular   speed   is  dependent   on  size    of  the gas molecule    and temperature.    The higher  the

temperature,    the higher  the molecular   speed.  The smaller the molecule    is, the higher  the

molecular   speed.  So  helium  is  a   smaller molecule    than    argon,  and the sample  at  100°C   would

have    the highest molecular   speed.

2 . E

The lower   the temperature is, the lower   the kinetic energy. Sample  E   has the lowest

temperature and therefore,  the lowest  kinetic energy.

3 . A

The ideal   gas equation    can be  used    for the relationship    among   volume, temperature,    and

pressure.   Volume  equals  the product of  the number  of  moles,  ideal   gas constant,   and

temperature (in Kelvin) divided by  the pressure.   The number  of  moles   is  constant;   the sample

with    the highest temperature would   have    the largest volume. So  sample  A   at  100°C   would

have    the largest volume. Since   pressure    is  inversely   proportional    to  volume, the lowest

pressure    would   have    the largest volume. The pressure    of  1   atm also    would   favor   the largest

volume.

4 . C

Bromine is  the only    nonmetallic element that    is  liquid  at  room    temperature.    It  is  one of  five

elements    that    are liquid  at  or  near    room    temperature (the    others  are the metals  cesium,

francium,   gallium,    and mercury).

5 . A