Explanation

Vertical columns in the periodic table are called groups.

Horizontal rows are called periods.

Explanation

Isotopes are atoms of the same element (same number of protons/nuclear charge) but different masses (different number of neutrons).

Explanation

Conductance (the ability to conduct electricity) generally increases with temperature for electrolytes (e.g., ionic solutions).

Because higher temperature enhances ion mobility and dissociation.

Explanation

In HNO₃ (nitric acid):

Hydrogen (H) = +1

Oxygen (O) = -2 (×3 = -6)

Let nitrogen = x

So, +1 + x + (−6) = 0

⇒ x = +5

Nitrogen has an oxidation state of +5 in HNO₃.

Explanation

Formalin (a solution of formaldehyde gas in water, typically 37-40%) is widely used as a preservative for biological specimens (e.g., in museums, labs, and medical settings).

It fixes tissues by cross-linking proteins, preventing decay and maintaining structure.