Sweet Apples and Oranges Flashcards
What are three diffusion experiments?
- Potassium manganate and water (in beaker) - Ammonia and Hydrogen Chloride (forms a white ring of ammonium chloride, nearer HCl as ammonia particles are smaller and lighter so diffuse faster) - Bromine gas and air (in a jar with a glass plate)
Simple distillation is used for…
separating a liquid from a solution, have to have very different BPs
Fractional distillation is used for…
separating a mixture of liquids with similar BPs
What is an isotope?
different forms of the same element which have the SAME no. protons and a DIFFERENT no. neutrons
The Periodic table is an arrangement of elements in order of ….
increasing atomic number
How do you find out the relative formula mass (Mr) of something?
Add up all the mass numbers
What is Empirical formula?
the simplest formula which tells you the ratio of different elements in a compound
What is Molecular formula?
tells you the actual number of atoms of each element in a molecule
How do you calculate percentage yield?
percentage yield = (actual yield (g) / theoretical yield (g)) x 100
moles in gas
moles = volume (dm3) / 24
moles in terms of conc
moles = concentration (mol/dm3) x volume (dm3)
What’s the electrical conductivity of Ionic compounds?
- only conduct electricity when molten or in solution
as when solid, ionic compounds are in a strict lattice structure and don’t have any free electrons. When the electrons are free to move when molten or in solution, they can carry an electric current and so therefore conduct electricity.
What’s the electrical conductivity of Metallic compounds?
- the sea of delocalised electrons in metallic bonding means that metals are good conductors of electricity and heat
What’s the electrical conductivity of Covalent compounds?
- covalent compounds don’t contain ions as they make bonds by sharing electrons, so don’t have any free charge carries and can’t carry an electric current.
APART FROM GRAPHITE, which has free electrons so is a good electrical conductor
What is ionic bonding?
a strong electrostatic attraction between oppositely charged ions
Why do ionic compounds have high melting and boiling points?
because of the strong electrostatic forces of attraction between oppositely charged ions
What is the relationship between ionic charge and the MP and BP of an ionic compound?
The bigger the difference in charge, the stronger the attraction: if you have + and - ions they will have a weaker bond than +3 and -3 ions.
The stronger the attraction, the harder it is to break the bonds, this means that the melting and boiling points will be higher. So the bigger the charge of an ion, the higher the melting and boiling point.
What’s an ionic crystal?
a giant 3D lattice structure held together by the strong attraction between oppositely charged ions
draw a diagram to represent the positions of the ions in a crystal of sodium chloride
alternating Na+ and Cl- ions in a 3D lattice
What is covalent bonding?
a strong attraction between the bonding pair of electrons and the nuclei of the atoms involved in the bond
What are the two forms of covalent substances?
Simple molecular substances and giant covalent structures
What are giant covalent structures?
like giant ionic structures but there are no charged ions.
- all the atoms are bonded together with very strong covalent bonds.
- don’t conduct electricity (apart from graphite)
- insoluble in water
Simple molecular substances are normally …. or … at room temperature
gases or liquids
Why do simple molecular substances have low MPs and BPs?
While the atoms within a molecule have very strong bonds, the forces of attraction between the molecules themselves are very weak.
This means that the INTERMOLECULAR forces are very WEAK and the MP and BPs are very low.
Why do giant covalent substances have high MPs and BPa?
- there are lots of strong covalent bonds so you need a lot of energy to break them, meaning high MP and BP
