Index Properties MCQ with answer and solution

Concept

Specific gravity of soil solids (G) is found in the lab using a pycnometer or a density bottle.

Formula

G = (W₂ - W₁) / [(W₂ - W₁) - (W₃ - W₄)]

Step-by-step solution

1. Take the empty pycnometer weight W₁. 2. Add dry soil and weigh: W₂. 3. Fill with soil + water and weigh: W₃. 4. Fill with water only and weigh: W₄. 5. Use G = (W₂ - W₁) / [(W₂ - W₁) - (W₃ - W₄)]. 6. So the method is the pycnometer method, option A.

Explanation

The pycnometer method compares the weight of soil solids with the weight of an equal volume of water. This gives the specific gravity of the soil solids. The density bottle method works the same way and is used for fine soils.

Why the other options are wrong

B: Hydrometer analysis gives the grain size of fine soils. C: Sieve analysis gives the grain size of coarse soils. D: The calcium carbide method gives the water content quickly.

Shortcut

Specific gravity = Pycnometer or density bottle.

Common mistake

Choosing hydrometer because it also uses a specific gravity value in its calculation.