G.K. (General Science) - 23

A pure substance consists of only one type of matter or substance, whereas a mixture contains multiple substances.

Highly reactive metals like potassium, sodium, and calcium are extracted from their molten chlorides via electrolysis because they are too reactive to be reduced by carbon.

Aluminium is extracted from its ore, bauxite, which is primarily aluminium oxide, through the Hall-Heroult process involving electrolysis of molten oxide.

Sodium metal is obtained by the electrolysis of molten sodium chloride (Downs process). Aqueous sodium chloride would result in the production of hydrogen gas instead of sodium metal.

In a suspension, particles are large enough to be seen with the naked eye and are typically larger than 100 nanometers (10^-7 meters).

The electrolysis of an aqueous solution of sodium chloride (brine) produces sodium hydroxide, chlorine gas, and hydrogen gas. This is known as the chlor-alkali process.

Calcination is the process of heating an ore strongly in the absence of air to convert carbonates into metal oxides. Roasting, by contrast, involves heating in the presence of excess air.

A homogeneous mixture is defined by its uniform composition and properties throughout. Heterogeneous mixtures have non-uniform compositions.

Zinc blende is a common mineral ore of zinc, and its chemical formula is zinc sulfide, ZnS.

Manganese and chromium oxides are reduced to their respective metals using aluminium powder as a strong reducing agent; this is a thermite-type reaction.

A solution where the solvent is not water is classified as a non-aqueous solution. Aqueous solutions specifically use water as the solvent.

In a solution, the substance being dissolved is the solute, while the substance doing the dissolving is the solvent.

A solution is defined as a homogeneous mixture of two or more substances. It consists of a solute dissolved in a solvent.

An unsaturated solution is one that can still dissolve more solute at a given temperature. A saturated solution has reached its maximum capacity.

The reduction of metal oxides by aluminium is highly exothermic, meaning it releases a significant amount of heat, often enough to keep the metal in a molten state.

The reduction of metal oxides using aluminium powder as a reducing agent is specifically referred to as the thermite reaction.

In a true solution, the solute particles are very small, typically less than 1 nanometer (10^-9 m) in diameter, often around 10^-10 m.

Barium sulfate is used as a radiocontrast agent in X-ray imaging of the digestive tract because it is opaque to X-rays and insoluble.

Colloidal particles are intermediate in size between true solutions and suspensions, typically ranging from 1 nanometer to 100 nanometers (10^-9 to 10^-7 m).

Carbon, aluminium, and sodium are all strong reducing agents used in metallurgy. Iron is generally not used as a reducing agent for these oxides, as it is less reactive than the others.

Electrophoresis is the phenomenon where charged colloidal particles move toward an oppositely charged electrode when an electric field is applied.

Metals like zinc are moderately reactive and cannot be extracted from their ores by heat alone; they require a chemical reducing agent like carbon.

The Tyndall effect is the scattering of light by particles in a colloid or suspension. A true salt solution has particles too small to scatter light.

Roasting is the process of heating a sulfide ore in the presence of excess air to convert it into a metal oxide.

Air is a homogeneous mixture of gases. Milk, smoke, and other colloids or suspensions are heterogeneous mixtures.