koncentracije

Koncentracije is the plural form of concentration in several South Slavic languages and is used in different fields to describe how much of a substance is present in a given amount of material or space. In science, concentration usually implies a ratio or fraction describing the amount of solute relative to solvent, solution, or mixture. In psychology and everyday language, concentration also refers to the mental ability to focus attention on a task.

In chemistry, common concentration measures include molarity (M), molality (m), mole fraction (χ), mass fraction (w), and parts per million (ppm). Molarity is moles of solute per liter of solution (M = n_solute / V_solution). Molality is moles per kilogram of solvent. Mole fraction is the ratio of moles of a component to total moles. Mass fraction is the mass of solute divided by total mass. ppm expresses solute mass per million parts of solution.

Molarity can vary with temperature because volume expands or contracts, whereas molality is temperature-independent. Activity, not concentration alone, often governs behavior in solutions, especially for strong electrolytes.

Applications include controlling reaction rates and equilibria in chemistry, determining contaminant levels in air or water, and interpreting data in medicine and industry. In psychology, concentration describes sustained attention and can be influenced by fatigue, distraction, and motivation.

Other uses include describing the concentration of populations, industries, or resources in geography and economics, and describing the density of pollutants in environmental science.