CHEMISTRY GLOSSARY

Froude number    →   Froudova značajka

Froude number (Fr) is a dimensionless quantity used in fluid mechanics, defined by

where v is velocity, l is length, and g is acceleration due to gravity.

ideal gas law    →   jednadžba stanja idealnog plina

The generalized ideal gas law is derived from a combination of the laws of Boyle and Charles. Ideal gas law is the equation of state

which defines an ideal gas, where p is pressure, V molar volume, T temperature, and R the molar gas constant (8.314 JK^-1mol^-1).

ideal solution    →   idealna otopina

Ideal solution is a solution in which solvent-solvent and solvent-solute interactions are identical, so that properties such as volume and enthalpy are exactly additive. Ideal solutions follow Raoult’s law, which states that the vapour pressure p_i of component i is p_i = x_i p_i^*, where x_i is the mole fraction of component i and p_i^* the vapour pressure of the pure substance i.

Ilkovic equation    →   Ilkovičeva jednadžba

Ilkovic equation is a relation used in polarography relating the diffusion current (i_d) and the concentration of the depolarizer (c), which is the substance reduced or oxidized at the dropping mercury electrode. The Ilkovic equation has the form

Where k is a constant which includes Faraday constant, π and the density of mercury, and has been evaluated at 708 for max current and 607 for average current, D is the diffusion coefficient of the depolarizer in the medium (cm²/s), n is the number of electrons exchanged in the electrode reaction, m is the mass flow rate of Hg through the capillary (mg/sec), and t is the drop lifetime in seconds, and c is depolarizer concentration in mol/cm³.

The equation is named after the scientist who derived it, the Slovak chemist, Dionýz Ilkovič 1907-1980).

inertial reference frames    →   inercijski referentni sustavi

When two frames of reference are moving relative to each other at constant velocity, they are said to be inertial reference frames. The observers from two such inertial frames measure, in general, different velocities of a moving particle. On the other hand, they measure the same acceleration for the particle. The laws of physics must have the same form in all inertial reference frames (the principle of invariance).

potential energy    →   potencijalna energija

Potential energy (E_p) is the energy stored in a body or system as a consequence of its position, shape, or state (this includes gravitation energy, electrical energy, nuclear energy, and chemical energy). Gravitational potential energy is the energy associated with the state of separation between bodies that attracts each other via gravitational force. Elastic potential energy is the energy associated with the state of compression or extension of an elastic object. Thermal energy is associated with the random motions of atoms and molecules in a body.

Rayleigh number    →   Rayleighova značajka

Rayleigh number (Ra) is a dimensionless quantity used in fluid mechanics, defined by

where l is length, g is acceleration of gravity, α is cubic expansion coefficient, T is temperature, ρ is density, η is viscosity, and a is thermal diffusivity.

sediment    →   sediment

1. Sediment is a fragmental material that originates from weathering of rocks and is transported by, suspended in, or deposited by water or air or is accumulated in beds by other natural agencies. When solidified, sediments form sedimentary rocks.

2. Strictly, sediment is a solid material that has settled down from a state of suspension in a liquid.

specific weight    →   specifična težina

Specific weight (γ) is defined as the ratio between the weight of a mass element, Δm, and the volume, ΔV, occupied by that element. As density (average) is defined as the ratio of a mass element and its volume, specific weight is equal to:

where g is gravitational acceleration.

spectrophotometer    →   spektrofotometar

Spectrophotometer is an instrument for measuring the amount of light absorbed by a sample.

The absorption of light by a substance in a solution can be described mathematically by the Beer-Lambert law

where A is the absorbance at a given wavelength of light, ε is the molar absorbtivity or extinction coefficient (L mol^-1 cm^-1), unique to each molecule and varying with wavelength, b is the length of light path through the sample (cm), and c is the concentration of the compound in solution (mol L^-1).