14. (i) A farmer prepared 1% solution of copper sulphate using iron rod as the
stirrer for preparing Bordeaux mixture. Next day he noticed that the blue colour
almost disappeared and the iron rod get coated with reddish brown material.
a) What is the reddish brown material deposited on the iron rod?
b) Account for the colour change of the solution.
c) Justify the above phenomenon as a redox reaction.
(ii) Justify why density of ice is lower than that of water.
(iii) Hydrogen reacts with most of the metals and non metals to form hydrides.
Elements in which one of the following group groups of the periodic table do not
form hydrides?
i) Groups 15, 16, 17 ii) Group 18 iii) Groups 7, 8, 9 iv) Group 14
kindly answer
Answers
Answer:
the year 1761, Schulthez first used the copper sulphate for the seed treatment of Wheat diseases. Later on Prevost termed the copper as fungicide. In 1882, Millardet in France (Bordeaux University) accidentally observed the efficacy of the copper sulphate against the downy mildew of grapes caused by Plasmopara viticola. When copper sulphate was mixed with lime suspension, it effectively checked the disease incidence. The mixture of copper sulphate and lime was named as “Bouillie Bordelaise” (Bordeaux Mixture).
The original formula developed by Millardet contains 5 lbs of CuSO4 + 5lbs of lime + 50 gallons of water. The chemistry of Bordeaux mixture is complex and the suggested reaction is: CuSO 4 + Ca (OH) 2 = Cu(OH) 2 + CaSO 4
The ultimate mixture contains a gelatinous precipitate of copper hydroxide and calcium sulphate, which is usually sky blue in colour. Cupric hrdroxide is the active principle and is toxic to fungal spores.
Bordeaux mixture is generally accepted even in organic cultivation. It is easy to prepare and can be locally prepared by farmers themselves.
Preparation of 1 % Bordeaux Mixture