IB Chem things I forgot

Things I have gotten wrong from IB Chemistry Past Paper

List the physical properties that will differ between isotopes

the lighter isotope will have a lower boiling point, melting point, + mass), density, but a greater rate of diffusion

How would you calculate relative atomic mass from mass spectrometry?

weighted atomic mass of the isotopes in the chemical element / 1/12 of the mass of one atom of carbon-12

Why is the amount of deflection in a mass spectrometer inversely proportional to the mass to charge ratio of the ions?

a larger mass means a particle is less able to adhere to the direction and pull of the magnetic field

How is abundance measured in a mass spectrometer

• by measuring the electric current generated when ions hit a negatively charged plate (the detector)

• the size of the current is directly proportional to the abundance

How is the atomic mass of each ion determined nin TOF mass spectrometry

• by the time taken for the ion to hit the detector

• all ions have equal kinetic energies, but heavier ions will take longer to reach the detector

Acid + base = ?

salt and water

What is the difference between an alkali and base?

• a base is any soluble or insoluble substance that can neutralise an acid, whereas an alkali is a solution of a base containing a soluble base

Suggest why releasing isotopes

containing more neutrons than the stable isotope into the environment can be dangerous.

radioactive/radioisotope(s)/give out radiation;

Define the ground state of an atom

the most stable electronic configuration of an atom, corresponding to its lowest possible energy state

Describe the bonding in metals

• electrostatic attraction

• between a lattice positive metal ions and a sea of delocalised electrons

List the types of EM radiation given out corresponding to the energy levels

• Small energy difference means a long wavelength and thus low energy - usually infrared

• Medium energy difference means visible light - Balmer series (from above n = 2 down to n = 2)

• Large energy difference means a short wavelength and thus high energy - usually UV (Lyman series), for all transitions to n =1

Describe Hund’s law

• electrons fill orbitals with the same spin singly with parallel orbits before pairing up

• this configuration minimises electron-electron repulsion, leading to a more stable, lower energy state for the atom

Why are emission spectra line spectra

• energy levels are discrete

  • this means electrons can absorb light only of specific energies, so the spectra will not be an ombre

What is the convergence limit?

the point where the spectral lines become infinitely close to each other, marking the transition to ionisation energy

Where do the lines converge in the emission spectrum of hydrogen

at higher energy, so to the right of the spectrum