Define Molarity .Give one of its disadvantage.
Molarity is no. of moles of solute dissolved in one litre of the solution.it is represented as 'M'.Thus a solution containing one gram mole of solute per litre of solution is said to be 1 molar solution. molarity = no. o f moles of solute /volume of solution in litres its disadvantage is, it changes with change in temerature as the liquid volume may change with change in temperature.
what is the reactivity order of halogen acids(HI, HCl , HBr ) on alcohol?Give reason also.
HI>HBr>HCl is the reactivity order of halogen acids on alcohol. Because the bond dissociation energy is lowest for HI and the bond can easily be broken . It is greater for HBr and Maximum for HCl. As we move down the periodic table the size of atom increases and its ability to hold the bond between last electron with the hydrogen ion also weakens and thus bond dissociation energy is less.
Why does metallic character increase down the periodic table?
Metals are electropositive in nature. i.e they have tendency to acquire positive charge by losing electrons. As we move down the periodic table ,the atomic size increases due to increase in atomic number and new shells added. The distance of last electron from the nucleus increases as we move down the periodic table,hence it becomes easier for the metal to lose its last electron to acquire positive charge . Since the electropositivity increases down the group ,hence the metallic character also increases down the group.