Part a: we can determine the purity of solid materials by using calorimetry. a gold ring (for pure gold, specific heat = 0.1291 j⋅g−1⋅k−1 ) with mass of 10.5 g is heated to 78.3 ∘c and immersed in 50 g of 23.7 ∘c water in a constant-pressure calorimeter. the final temperature of the water is 31.0 ∘c.

Thus, the question would probably ask if the ring of gold is actually pure gold. For this, first there is a need to calculate the specific heat capacity of the calorimeter. If this equivalent to the specific heat for pure gold, then the gold ring is pure fold.

Qwater = mCdt = (50 g) × (4.18 J/gC) (31 - 23.7) = 1525.7 J

On the basis of conservation of energy,

Qwater = Qcalorimeter = mCdT = 1525.7

1525.7 = (10.5) (C) (78.3 - 31)

C = 3.072 J/gC

As the specific heat of the calorimeter is not equivalent to that of the pure gold (0.1291 J/gC), then the gold ring is not pure.

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.