________ is a donor impurity for semi-conductors?

Pick out the endothermic reaction out of the following?

Manufacture of phthalic anhydride uses ________ as a catalyst?

A fertilizer plant is classified as a gas based fertilizer plant, when it uses ________ gas as a source of hydrogen for the manufacture of ammonia?

What is the shear rate at the pipe wall, in case of laminar flow of Newtonian fluids in a pipe of diameter ‘D’ & length ‘L’ incurring a pressure drop ‘Δp’ with average velocity ‘Vavg’?

The life of a ball bearing is inversely proportional to________?