Give reasons for each of two following.
(i) Use of molybdenum in the manufacture of ammonia
(ii) Air dissolved in water is different from ordinary air
(iii) Mg continues to burn in carbon dioxide however CO₂ does not supports combustion
(iv) For welding of two metallic pieces, an oxyhydrogen flame is used
(v) Need of mentioning temperature and pressure while stating its volume
Answers
Answer:
also too big question...............
The reasons for above questions are:---
(i)The use of molybednum in manufacture of ammonia is it act as promoter for chemical reaction and improve efficiency and rate of reactions so is known as promoter. It improves efficiency of catalyst iron used and hence help in increasing yield of ammonia.
(ii)Air which is dissolved in water is different from ordinary air as ordinary air is mixture of gases like nitrogen, carbon dioxide, sulphur, oxygen etc, so when this air is dissolved in water so these gases react with water to form different compounds.
CO2 in air combine with water to form carbonic acid,and the solubilty of Co2 in water is much higher than any other gas so concentration of CO2 in ater increases which was less in ordinary air.
Similarly Nirogen form nitric acid and concentration is least in water whereas concntration of nitrogen is most in ordinary air. So ordinary air is different from air which is dissolved in water.
(iii)Mg burns in CO2 even if CO2 is non supporter of combustion as magnesium is very reactive metal and has greater affinity towards oxygen which it gets from CO2. So magnesium burns brightly in air but burns with black sloth in CO2 which is of carbon. Reaction is:-
2Mg + CO2-------> 2MgO + C
(iv)An oxyhydrogen flame is used for welding as it is mixture of hydrogen and oxygen in 2:1, the mixture melts the metals as it is used to attain ignition temperature. When ignited it melts metals with release of energy and this energy is used in combing metals and also melted metals are easy to combine or weld. Hence we use oxyhydrogen flame.
(v)It is important to state the temperature and pressure of gas while stating its volume because of the fact that gas occupies volume based on temperature and pressure as at high temperature gas molecules gain kinetic energy and hence have tendency to expand and occupy more space or volume.
Similarly at high pressures the gas molecules are compressed and hence take less space. Since temperature and pressure give information of volume occupied by gas so it is important to mention these properties while stating volume of gas.