A Level Chemistry ....
Practice: YT: Unit 4 January 2022 - A2 Chemistry - Dr Hanaa Assil
A) The Born-Haber cycle is a classic approach to measure the reaction energies. The cycle is mostly concerned with the formation of an ionic solid from the metals (Group I or Group II) when reacted with a halogen or a non-metallic element like oxygen.
B) The Born Haber cycle was introduced in the year 1919 by German scientists Fritz Haber and Max Born. The Born Haber cycle is mainly used to calculate the lattice energy. It also involves several steps or processes, such as electron affinity, ionization energy, sublimation energy, the heat of formation and dissociation energy.
C) The standar molar enthalpy change of atomisation is defined as the enthalpy change when 1 mol of an element in its standard state is atomised to produce 1 mol of gaseous atoms. By "standard state" we mean the state the element is naturally found, for example for Chlorine it is Cl2(g) and for Sodium it is Na(s).
D) The oxygen family, also called the chalcogens, consists of the elements found in Group 16 of the periodic table and is considered among the main group elements. It consists of the elements oxygen, sulfur, selenium, tellurium and polonium.
E) Why is group 16 called chalcogens?
-Group-16 elements are also called chalcogens. They are called so because most of the copper ores have copper in the form of oxides and sulphides. They also contain small amounts of selenium and tellurium. The ores of copper are called 'chalcos' in Greek.
F) The first electron affinity is the energy released when 1 mole of gaseous atoms each acquire an electron to form 1 mole of gaseous -1 ions. It is the energy released (per mole of X) when this change happens. First electron affinities have negative values.
G) The enthalpy of hydration ΔHhyd is the enthalpy change when one mole of gaseous ions is dissolved in water to give one mole of aqueous ions and a solution of infinite dilution. Infinite dilution means that if you add any more water to a solution, it is so diluted that the concentration will not change.
H) The equilibrium constant is the ratio of the concentrations raised to the stoichiometric coefficients. Therefore, the unit of the equilibrium constant = [Mole L-1]△n. Where, ∆n = sum of stoichiometric coefficients of products – sum of stoichiometric coefficients of reactants.
I) A diprotic acid is an acid that has two hydrogen ions in its molecule. Diprotic acids are capable of donating a total of two hydrogen ions to other molecules.
J) Ketoprofen is a nonsteroidal anti-inflammatory drug (NSAID) that is used to treat pain, inflammation, swelling, stiffness, and joint pain. This medicine is available only with your doctor's prescription. This product is available in the following dosage forms: Capsule, Extended Release.
K) What are chiral centers? A chiral centre is an atom that has four different groups bonded to it in such a manner that it has a nonsuperimposable mirror image. The term "chiral centre" has been replaced by the term chirality centre. In the molecule below, the carbon atom is a chirality centre. ... https://socratic.org/organic-chemistry-1/r-and-s-configurations/introduction-to-chirality-and-chiral-centers
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