Solution:
The colour of transition-metal compounds is normally associated with d-d transitions. However, some transition metal compounds show intense colour in solution in spite of absence of d-electrons. For example, the orange colour of TiBr4, yellow colour of CrO42-, orange colour of Cr2O27-, intense red colour of [Fe(SCN)4] and deep purple of MnO4 are not due to d—d transitions. In the case of MnO4 ion, the color is due to charge transfer and not due to d-d transitions.

Solution:
By-product obtained by soap industry is glycerol.

Solution:
Gypsum is calcium sulfate which is essential to the sustainability of most irrigated soils. Irrigated land eventually leads to sodicity and salinity unless extreme care is taken. It improves sodic (saline) soils by removing sodium from the soil and replacing it with calcium.

Solution:
The ionisation energy for the hydrogen atom can be written as: Ionisation energy = energy in first orbit - energy in infinite orbit Ionisation energy = ​ E = -E0 / n2 , where E0  = 13.6 eV (1 eV = 1.602×10-19  Joules) and n = 1,2,3… and so on. The difference in energy = Einfinity - E1 so the ionisation energy from the ground state = x KJ = 0-( -E0 /12 ) = E0 The energy required to jump the elctron from second to the third stage is:

Solution:
Methyl orange is a pH indicator frequently used in titrations. It is often used in titrations because of its clear and distinct colour change. Because it changes colour at the pH of a mid-strength acid, it is usually used in titrations for acids. In a solution becoming less acidic, methyl orange moves from red to orange and finally to yellow with the reverse occurring for a solution increasing in acidity. The entire colour change occurs in acidic conditions. In an acid it is reddish and in alkali it is yellow

Solution:
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most nonspecialty grout. It usually originates from limestone. It is a fine powder produced by grinding Portland cement clinker (more than 90%), a limited amount of calcium sulfate (which controls the set time) and up to 5% minor constituents. Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates, the remainder consisting of aluminium- and iron-containing clinker phases and other compounds.

Solution:
The compound zinc oxide (ZnO) is called philosopher's wool. Alchemists, as part of their rituals, would burn zinc in air and collect the residue, which formed into white woolly tufts. They called it lana philosophica in Latin, meaning philosopher's wool.