Which among the following statement(s) is (are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to 

(i) the formation of silver by decomposition of silver chloride 

(ii) sublimation of silver chloride 

(iii) decomposition of chlorine gas from silver chloride 

(iv) oxidation of silver chloride. 

Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by the liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed? 

(i) It is an endothermic reaction 

(ii) It is an exothermic reaction 

(iii) The pH of the resulting solution will be more than seven 

(iv) The pH of the resulting solution will be less than seven 

Which of the following are combination reactions? 

(i) $2{\mathrm{KClO}}_3\stackrel{\mathrm{Heat}}{\to }2\mathrm{KCl}+3{\mathrm{O}}_2$

(ii) $\mathrm{MgO}+{\mathrm{H}}_2\mathrm{O}\to \mathrm{Mg}{\left(\mathrm{OH}\right)}_2$

(iii) $4\mathrm{Al}+3{\mathrm{O}}_2\to 2{\mathrm{Al}}_2{\mathrm{O}}_3$

(iv) $\mathrm{Zn}+{\mathrm{FeSO}}_4\to {\mathrm{ZnSO}}_4+\mathrm{Fe}$

Chemically rust is