SAT Subject Test Chemistry,10 edition

8 . 5.81    ×    10 –23 g/atom, 5.31    ×   10–23 g/molecule

The mass    of  a   single  atom    is  determined  by  dividing    the atomic  weight  by  Avogadro’s  number.

Therefore,  the mass    of  a   chlorine    atom    is

The mass    of  an  oxygen  molecule    (O 2 )  is  similarly   determined  by  dividing    the molecular   weight

of  oxygen\ by  Avogadro’s  number.

9 . 5.5

From    the balanced    equation,   it  can be  seen    that    for every   mole    of  ammonia produced,   0.5 mol

Ag(NH 3 ) 2 +   is  needed  (a  ratio   of  2:1).   So, to  produce 11  mol ammonia,    5.5 mol Ag(NH 3 ) 2 +   is

required    and since   a   mole    of  Ag(NH 3 ) 2 +   contains    1   mole    of  Ag, 5.5 moles   of  Ag  are required.

10 . C
In order to answer this question, you must use the law of conservation of mass, which says that
the mass of the products must be equal to the mass of the reactants. Therefore, if 5.8 g of
Ag(NH 3 ) 2 + is allowed to dissociate to form 1.4 g of ammonia, 5.8 – 1.4 or 4.4 g of silver must be
formed. The following calculation is used to determine the number of moles of silver that are
formed.

11 . 76.1%, 19.7%, 4.2%

The percent composition of  elements    in  a   compound    or  formula is  determined  by  dividing    the

mass    of  the element by  the total   formula weight  of  the compound.   Therefore,  in  the complex

ion,    Ag(NH 3 ) 2 +,  which   has a   formula weight  of  142 g/mol,  the percent compositions    of  Ag, N,

and H   are as  follows: