Lattice energies, trends & Born Haber Cycle

Lattice energy is defined as the energy required to separate a mole of an ionic solid into gaseous ions. Na+(g) + Cl–(g)  NaCl(s) Ho = -787.3 kJ/mol Born Haber cycle for NaCl: Lattice energy cannot be measured empirically, but it can be calculated using electrostatics or estimated using the Born-Haber cycle. Two main factors that contribute to […]

23 elements of symmetry in cubic crystal

Plane of symmetry: It is an imaginary plane which passes through the molecule and divides it into two equal portions which are exactly the superimposable mirror images of each other. An axis of symmetry can only passes through (1) mid-points of two opposite edges. (As a cube has 12 edges, there are 12÷2=6 axes of […]

Project IIT- Hydrogen spectrum Wavelengths -PhysiChemistry

Regarding hydrogen spectrum- Don’t forget to remember first and last lines of Lyman, Balmer series and Paschen series.   For Balmer series, remember second, third and fourth line as well. Last line wavelength is also called series limit. It can be calculated by taking n2 as infinity. Last line wavelength is the shortest wavelength and hence […]

FeCl3 stable but FeI3 is highly unstable.

Problem Fact- FeCl3 is stable but FeI3 is highly unstable. Fe forms FeF3 ,FeCl3 and FeBr3, but not FeI3. FeI3 is unstable, decomposes to FeI2 and I2. Cul2 is unstable, decomposes to CuI (Or Cu2I2) and I2. FeCl3 + 3KI = FeI3 + 3KCl ;  FeI3 = FeI2 + I2   Fe2O3 + 6HI ⟶ 2FeI2 + I2 + 3 […]