(A) Using the reactions below, write out the chemical expression for the fraction of all species that

would be [Sn2+] (note this form does not need to be solved for K values, just the compounds themselves).

Sn2+(aq) + F-(aq) %u2190%u2192 SnF+(aq) Kf1 = 4.0 x 10^3

SnF+(aq) + F-(aq) %u2190%u2192 SnF2 (aq) Kf2 = 2.7 x 10^3

SnF2 (aq) + F-(aq) %u2190%u2192 SnF3-(aq Kf3 = 9.1 x 10^1

a for [Sn2+] = ________________________________

(B) The following expression shows the equilibrium for the second reaction. However, the [SnF+] term may be difficult to determine.

(i) So, with help from the first reaction, rewrite that Kf2 expression in terms of only Sn2+; F-; SnF2 and Kf values.

(ii) Then rearrange that new form of the expression to solve for [SnF2]

Kf2 = [SnF2 ]/ [SnF+ ][F-]

(i) New form of Kf2 =

(ii) THEN [SnF2] =