GK (General Science)

Covalent compounds consist of molecules held together by shared electrons; they do not dissociate into ions in solution and therefore do not conduct electricity, making them non-electrolytes.

Covalent compounds lack mobile charge carriers because they do not form ions when dissolved or melted. Without free-moving charged particles, electricity cannot flow through these compounds.

The external openings of the nasal cavity are anatomically known as nostrils.

Both HCl (hydrogen chloride) and ammonia (NH3) are polar covalent compounds due to the electronegativity difference between the bonded atoms. Since both are polar, option D is the correct choice.

The lungs are protected by a double-layered serous membrane called the pleura, which reduces friction during breathing.

Hydrogen chloride gas is a covalent compound that ionizes when dissolved in water to form hydrochloric acid, which then conducts electricity. Alcohol and carbon tetrachloride do not ionize in water.

 Trachea is supported by rings of soft bones called cartilage.

Covalent compounds are generally non-polar or weakly polar, making them more soluble in organic solvents (like benzene or ether) than in water, which is a highly polar solvent.

The pharynx is the muscular tube that connects the mouth and nasal cavity to the esophagus and the larynx (windpipe).

The trachea bifurcates into two primary bronchi, which lead into the left and right lungs.

Inside the lungs, the bronchi branch into smaller tubes called bronchioles, which eventually terminate in the alveoli.

Ionic compounds conduct electricity in molten or aqueous states due to free ions, whereas covalent compounds generally do not. This makes conductivity a primary distinguishing test.

The Earth's crust is the primary source for most metals, which are extracted from minerals and ores found within it.

Noble metals like gold, silver, and copper are chemically unreactive and can be found in their native or free state in nature.

Alveoli are surrounded by a dense network of pulmonary capillaries to facilitate the exchange of oxygen and carbon dioxide.

Due to their high reactivity, most metals readily react with other elements in nature and are therefore found as compounds (oxides, sulfides, carbonates, etc.).

The standard medical reference range for hemoglobin in healthy adult males is typically 13.5 to 17.5 g/dL and for females 12.0 to 15.5 g/dL, making 12 to 18 g/dL the most accurate range provided.

Xylem tissue located within the root structure is specifically referred to as root xylem.

The endodermis is the innermost layer of the cortex in plant roots, which surrounds the vascular cylinder (stele).

Highly reactive metals like potassium, sodium, and calcium are never found in their free state; they are always found as compounds.

Metals above copper in the reactivity series are sufficiently reactive to form stable compounds with oxygen, sulfur, or carbon in nature.

Minerals are naturally occurring inorganic substances found in the Earth's crust from which metals can be extracted.

Xylem is the specialized plant tissue responsible for the upward transport of water and dissolved minerals from the roots to the rest of the plant.

Mature human red blood cells and platelets lack a nucleus, while white blood cells (leukocytes) contain a nucleus and nucleolus.

An ore is a type of rock that contains sufficient minerals with important elements, including metals, that can be extracted for profit.