Definitions Flashcards
What is relative isotopic mass
It is the mass of one atom of the isotope relative to 1/12 the mass of one atom of carbon-12
What is relative atomic mass (Mr)
It is the weighted average of the isotopic masses of one atom of an element relative to 1/12 the mass of one atom of carbon -12
What is relative molecular mass?
It is the wighted average of the masses of one molecule of a substance relative to 1/12 the mass of one atom of carbon -12.
What is relative formula mass?
It is the weighted average of the masses of one formula unit relative to 1/12 the masses of one atom ot carbon -12.
What is an empirical formula?
The empirical formula of a compound is the simplest formula that shows the simplest whole number ratio of the atoms of each element present in the compound.
What is a molecular formula?
The molecular fermula. of a compound shows the actual number of atoms of each element in one molecule of the compound. It is a simple multiple of the empirical formula and can only be obtained if the molar mass is known.
What is 1 mole of a substance?
1 mole of a substance is the amount of that substance which contains 6.02x10^23 particles. [Avogadros constant]
What is a disproportionate on reaction?
It is a redox reaction where a single substance is oxidized and reduced at the same time.
What is the Manganate titration colour change?
Purple (MnO4-) to colourless (end point) / faint pink (Mn2+)
What is the iodine thiosulfate titration color change?
Solution turns pale yellow after addition of starch
Solution turns colourless at end point
Basic assumptions when doing ideal gas / kinetic theory of gas ?
- A gas is composed of tiny particles that have negligible volumes compared to volume of container
- There are negligible intermolecular forces between gas particles
- Collisions are perfectly elastic and there is no net loss in Kinetic Energy between gas particles
What causes less deviation from ideal gas behavior? (Approaching ideal gas behavior)
- Low pressure: IMF negligible, total volume of particles negligible
- High temperature: sufficient KE to overcome IMF attractions: negligible.
* stronger IMF = stronger deviation
** larger molecular mass = stronger id-id
What is a metallic bond?
It is the electrostatic forces of attraction between metal cations and the sea of delocalised electron
How does metallic bond strength relate to
1. Cations of higher charge
2. Ionic radius
- Directly proportional (cation higher charge = increased MB strength)
- Inversely proportional (increased MB strength = smaller ionic radius)
What is an ionic bond ?
It is the electrostatic forces of attraction between oppositely charged ions in an ionic compound
What is a covalent bond?
It is the electrostatic forces of attraction of the positively charged nuclei of each bonding atom for the shared pair of electrons
Define bond energy
It is the energy required to break one mole of covalent bonds between atoms in a gaseous molecule
Define bond length
The distance between the nuclei of the two atoms covalently bonded to each other
What affects the strength of covalent bonds?
- Bond order: triple > double > single
- Effectiveness of orbital overlap: decreases with larger atomic size (Mr)
Describe diamond’s structure and bonding
Each carbon atom forms strong covalent bonds with 4 carbon atoms in a 3D tetrahedral arrangement in a giant covalent lattice structure
Describe graphites structure and bonding
Each carbon atom forms strong covalent bonds with 3 other carbon atoms in a 2 D layer of hexagonal carbon rings with weak intermolecular forces of attraction between graphene layers + electric conductivity from highly mobile pi electrons
Factors affecting strength of id-id
- Size of electron electron cloud (ease of distortion) : larger Mr = larger cloud, dipoles more easily induced, more energy to overcome stronger id-id
- Surface area of contact: straight chain have larger surface area of contact
3 atoms that can have hydrogen bonding (IMF)
N, O, F
* protonic H / lone pair
Factors that affect hydrogen bonding strength
- Different number of H-bonds: more protonic H or lone pairs on NOF
- Polarity of H-(NOF) bond: more polar = stronger. Order: N<O<F
- Infra molecular H bonding may reduce the number of available H bonding sites for intermolecular bonding
What does the bond strength of ionic, metallic, and covalent bonds depend on?
Ionic: L.E.
Metallic:
1. No. Of electrons that can be delocalised
2. Inversely proportional to ionic radius
Covalent:
1. Bonds: Effectiveness of orbital overlap (dependent on atomic radius / Mr) & bond order (1-3)
2. IMF: id-id, pd-pd, h bonding (broken in heating)
