Index Properties MCQ with answer and solution

Concept

In the shrinkage limit test, mercury displacement is used to find the volume of the dry soil pat. The density of mercury is about 13.6 g/cc.

Formula

V_d = (mass of displaced mercury) / ρ_Hg, where ρ_Hg = 13.6 g/cc

Step-by-step solution

1. In the shrinkage limit test, the dry soil pat is pushed into a cup full of mercury. 2. The displaced mercury is weighed. 3. Volume of dry pat = mass of displaced mercury / density of mercury. 4. Density of mercury = 13.6 g/cc (specific gravity 13.6). 5. So the answer is (B).

Explanation

Mercury is used because soil does not absorb it and it does not stick to the soil pat. Its density is about 13.6 g/cc, so its specific gravity is 13.6.

Why the other options are wrong

A: 14.6 g/cc is too high. C: 12.6 g/cc is too low. D: 15.6 g/cc is too high. Only 13.6 g/cc is the standard value for mercury.

Shortcut

Remember: specific gravity of mercury = 13.6.

Common mistake

Mixing up 13.6 with nearby numbers like 12.6 or 14.6.