Chemistry

21. Reaction of Metals with Water : Some metals like Na, K, Ca react with cold water vigorously to form hydroxide and liberate hydrogen gas. Some metals like Mg, Zn, Al react with hot water to form oxides and hydroxides and hydrogen gas. Some metals like Fe reacts with steam to form Fe₃O₄ and H₂(g). Some metals like Cu, Ag, Au, Hg, Pb and Pt do not react with water at all because they are less reactive than hydrogen. Let us perform the following experiment.
22. Reaction of Metals with Acids : Metals react with dilute acids to from salt and hydrogen gas. The metal replaces hydrogen of the acid to from salt. Let us perform experiment to show the reaction of metals with acids.
23. Aqua Regia : It is mixture of conc. HCl and conc. HNO₃ (nitric acid) in the ratio of 3 : 1. It can dissolve gold and platinum. Gold and platinum do not react with conc. HCl. They do not react even with conc. HNO₃ They dissolve in aqua regia. Aqua regia is a strong oxidising agent due to formation of NOCl (Nitrosyl chloride) and chlorine produced by reaction of two acids. Aqua regia (Latin word for royal water) is a highly corrosive and fuming liquid. Therefore, it should be kept away from eyes and skin.
24. Reaction of metals with solution of other metal salts : More reactive metal can displace less reactive metal from their salt solution. These reactions are called displacement reactions. Let is carry out these reaction experimentally.
25. Reason for difference in Reactivity of Metals :
We have observed with the help of experiments that some metals are less reactive whereas other metals are more reactive. Let us find out the reason why are some metals more reactive whereas other metals are less reactive.
Metals are those elements which can lose electrons easily. The reactivity of metals will depend upon how easily metal can lose electron and form positively charged ion. Metals have 1 to 3 electrons whereas non-metals have 4 to 8 electrons. hydrogen and Helium have one and two electrons respectively but still they are non-metals because they cannot lose electrons easily. Boron has three valence electrons but still it is non-metals.