To make benzene soluble cement, 60 g rosin is melted in an iron pot and 68 g beeswax and 12 g shellac are added. How much of the shellac should be taken to make 35 g cement?

Hint: This question requires knowledge of the stoichiometric reaction between the components of benzene soluble cement.

Complete step by step answer:
The total amount of benzene soluble cement formed from the combination of 60 g rosin, 68 g beeswax and 12 g shellac = $60+68+12=140$ g of cement.
So, for 140 g of benzene soluble cement, 12 g of shellac was required.
Therefore, for 35 g of cement, the amount of shellac = \[\dfrac{12}{140}\times 35\]= 3 g of shellac.Hence the answer is 3 grams of shellac required to make 35 grams of benzene soluble cement.

Note:
-Rosin is a solid form of resin obtained from coniferous trees such as pine. It is semi-transparent and varies in colour from yellow to black. It has innumerable uses and some of them include usage in printing inks, varnishes, adhesives, soap, soda, soldering fluxes, and sealing wax. Rosin is made edible as esters of glycerol, mannitol, etc., and used as a chewing gum base. Besides chewing gum, rosin also serves as the base of a number of other substances.
-Shellac is also a resin just like rosin, and is secreted by a female bug on trees found in the forests of India and Thailand. It is sold as dry flakes and dissolved in alcohol to make liquid shellac that is used as a natural primer, sanding sealant, tannin blocker, etc.