Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Paper format. National Exams, May 2015 — 98-Civ-A3 Environmental Engineering. Three hours; closed book with one candidate-prepared double-sided aid sheet and an approved Casio or Sharp calculator. Seven problems of 20 marks each; any five constitute a complete paper and only the first five answers in the work book are marked, for a maximum of 100 marks. The complete Marking Scheme is printed on page 8 and is reproduced against each question below. All seven problems are solved here, because this set is a study resource rather than an examination script.
Reference texts.
Check: compound naming in Problem 1(i). The question names the spilled liquid “dipropylene glycol” but gives its formula as C3H8O2 and its quantity as 38 kg (500 mol). C3H8O2 has a molar mass of 76.09 g/mol, and 38 000 g / 500 mol = 76.0 g/mol — so the formula, the mass and the mole count agree exactly with each other. It is the name that is wrong: C3H8O2 is propylene glycol (dipropylene glycol is C6H14O3, 134.2 g/mol). The solution therefore uses the self-consistent set (500 mol, 76.09 g/mol) and notes the naming slip, as NOTE 1 on page 1 invites. Nothing in the answer depends on the name.