422 THE TRANSITION ELEMENTS
- The transition metals form complexes which are usually
different in kind and in stability from those formed by the non-
transition elements. Give reasons for these differences.
(Liverpool B.Sc., Part I) - A compound of cobalt has the formula Co(NH 3 )JCClr 0.500 g
of it was dissolved in 50.00 cm^3 M hydrochloric acid; the excess
acid required 40.00 cm^3 M sodium hydroxide solution to neutralise
it. Another 0.500 g portion of the compound was dissolved in water
and allowed to react with excess silver nitrate solution. 0.575 g of
silver chloride was precipitated.
(a) Calculate the number of moles of ammonia liberated from
0.500 g of the cobalt compound.
(b) Calculate the number of moles of chloride ion released from
0.500 g of the cobalt compound.
(Atomic weights: Ag = 108, Cl = 35.5).
(c) What values for x and y in the original formula do these results
suggest?
(Atomic weights: Co = 60, N = 14, H = 1).
(d) When the compound was decomposed before addition of
silver nitrate, the value of y was found to be 50% greater than
the value you have calculated. Offer an explanation for the
two values of y.
(e) Draw the structure of the complex.F ,_. , ^ 0 T
(Liverpool B.Sc., Inter)- In what ways do the chemical and physical properties of
zinc(II) differ from those of iron(II)? Account for these differences.
Explain what happens when
(a) copper(I) oxide is treated with dilute sulphuric acid,
(b) cobalt(II) chloride solution is treated with an excess of
concentrated ammonia solution and air is bubbled through
the mixture,
(c) an excess of a concentrated solution df aqueous ammonia is
added dropwise to an aqueous solution of nickel(II) chloride,
(d) an excess of an aqueous solution of potassium cyanide is
added dropwise to an aqueous solution of nickel(II) chloride.
(JMB, A)- (a) Outline the extraction of manganese from pyrolusite and
state one important use of the metal. Suggest a method for
the preparation of a solution of potassium permanganate
starting from manganese, stating the oxidation state of man-
ganese at each stage in the process.