Results 1–7 of 7 for Fajans%E2%80%99 rules
Fajans’ rules, formulated by American chemist of Polish origin. Kazimierz Fajans (1887-1975), indicating the extent to which an ionic bond has covalent character caused by polarisation of the ions. Covalent character is more likely if:
1. the charge of the ions is high;
2. the positive ion is small or the negative ion is large;
3. the positive ion has an outer electron configuration that is not a noble- gas configuration.
Gibbs phase rule is the relationship used to determine the number of state variables, usually chosen from among temperature, pressure, and species composition in each phase, which must be specified to fix the thermodynamic state of a system in equilibrium:
where C is the number of components in a mixture, P is the number of phases, and F is the degrees of freedom, i.e., the number of intensive variables that can be changed independently without affecting the number of phases.
Markovnikov’s rule: when an asymmetrical alkene reacts with a hydrogen halide to give an alkyl halide, the hydrogen adds to the carbon of the alkene that has the greater number of hydrogen substituents, and the halogen to the carbon of the alkene with the fewer number of hydrogen substituents.
Octet rule states that the chemical properties of the elements repeat on a regular basis with increasing atomic mass, and that the chemical properties of each eight element are similar. Since the inert gases, with the exception of helium have eight electrons in their outer shells, this stable electronic configuration is called the octet rule. In chemical reactions atoms of elements tend to react in such a way as to achieve the electronic configuration of the inert gas nearest to them in the periodic table. There are a number of exceptions to the octet rule.
Faraday constant (F) is the electric charge of 1 mol of singly charged positive ions.
where NA is Avogadro’s constant (6.022×1023 mol-1) and e is the elementary charge (1.602×10-19 C).
Measurements are not infinitely accurate: we must estimate measurement uncertainty. The number of significant figures is all of the certain digits plus the first uncertain digit.
Rules for significant figures:
0.0023 | has two significant figures |
0.109 | has three significant figures |
2.00 | has three significant figures |
70 | has one significant figure |
In addition and subtraction, the number of significant figures in the answer depends on the original number in the calculation that has the fewest digits to the right of the decimal point.
In multiplication and division, the number of significant figures in a calculated result is determined by the original measurement that has the fewest number of significant digits.
In a logarithm of a number, keep as many digits to the right of the decimal point as there are significant figures in the original number.
In an antilogarithm of a number, keep as many digits as there are digits to the right of the decimal point in the original number.
Silver coulometer consists of a platinum vessel which acts as a cathode and contains a solution of pure silver nitrate as an electrolyte (c(AgNO3) = 1 mol/L). A rod of pure silver enclosed in a porous pot acts as the anode. The current density at the anode should not exceed 0.2 Acm-2. After electrolysis, the electrolyte is taken out and the platinum vessel is washed, dried and weighed. The increase in the weight gives the amount of silver deposited (96500 C of electricity deposits 107.88 g of silver). From the mass of the silver deposited, the coulomb involved in the reaction can be calculated.
Generalic, Eni. "Fajans%E2%80%99 rules." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
Glossary
Periodic Table