Question (a) State your observation in each of the following cases :
(1) When dilute hydrochloric acid is added to sodium carbonate crystals.
(ii) When excess sodium hydroxide is added to calcium nitrate solution.
(ii) At the cathode when acidified aqueous copper sulphate solution is electrolyzed with copper electrodes.
(iv) When calcium hydroxide is heated with ammonium chloride crystals.
(v) When moist starch iodide paper is introduced into chlorine gas.​

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.

a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.

space exploration has led to the development and technological improvement of many everyday items. (if this answer is wrong i will find the right answer) : )