Question

You, the chemistry detective, have obtained a water-insoluble ionic compound with the formula XYZ3 where X represents a metal, and Y and Z are both nonmetals. Answer the questions below, identify the ionic compound and find its percent composition by mass. (25 points) a) The metal X is a member of transition metals of the 4th period. It is one of the three elements that have the highest electronegativity among the transition metals of the 4th period, but unlike the other two it does not react with acids. Use these facts, together with the Electronegativity table and the Metal Activity series (given below) to identify the metal: 6

Answer 1

XYZ₃ : Water -insoluble ionic compound ; X -metal ; Y,Z - Non-metal

(a) X -tansition metal of 4th period

3 elements of Highest electronegativity : Co , Ni, Cu

It does not react with acids. : metal activity series Cu is least reactive.

It is Cu.

(b) Charge on X (Cu) = +2

(c) Polyatomic anions (YZ₃) : CO₃^2- ; NO₃^-

(d) Non metal Z = O (same in both anions )

(e) Charge of Polyatomic anions (YZ₃) : CO₃^2- matches with metal ion charge . :CO₃^2-

(f) from Polyatomic anions (YZ₃) : CO₃^2- : Y = C

(g) XYZ₃ : CuCO₃ ( Water -insoluble ionic compound)

Copper carbonate.

(h) Percent composition by mass :XYZ₃ : CuCO₃

Total mass = 63.5 g/mol (Cu) + 12g/mol (C) + 3*16 g/mol (O) = 123.5 g/mol

Cu % by mass = (63.5/123.5 )*100 = 51.42 %

C % by mass = (12/123.5 )*100 = 9.72 %

O % by mass = (48/123.5 )*100 = 38.86 %