4th Form Flashcards
Why do high surface area increase rate of reaction?
More of the solid is exposed to the other particles
So there are more particles per unit volume
So the collision frequency is higher
So there are more successful collisions per unit time
Why does a higher concentration increase rate of reaction?
There are more particles per unit volume
So the collision frequency is higher
So there are more successful collisions per unit time
Why does a higher temp increase rate of reaction?
The particles have more kinetic energy
So the percentage of collisions with energy above activation energy is higher
So there are more successful collisions per unit time
Why does a catalyst increase rate of reaction?
They provide an alternative route with a lower activation energy
So the percentage of collisions with energy above activation energy is higher
So there are more successful collisions per unit time
Define covalent bonding
The electrostatic attraction between protons in two nuclei and a shared pair of electrons between them
Why do simple molecular covalent substances boil easily?
Although simple molecules contain very strong covalent bonds, there are also weak intermolecular forces (IMFs) between the molecules.
When simple molecular substances boil, it’s the weak IMFs which break
Why can a simple molecular substance not condunt electricity?
Electrical conductivity requires charged particles that can move freely
But in a simple molecular substance, there aren’t any charged particles
Why does diamond have a high melting point?
Covalent bonds are very strong
There are lots of bonds in the giant lattice
Lots of energy is required to break all the bond
Why can diamond not conduct electricity, but graphite can, since they are both types of carbon?
Diamond cannot conduct electricity, as there are no free moving charged particles, as all the electrons are stuck inside an atom or a bond. Graphite has free moving charged particles between the layers, so it can.
Name the structure and essential properties of an ionic bond.
Giant lattice
High mp/bp
Insulator when solid
Conductor when liquid
Conductor when in an aqeous solution
Name the structure and essential properties of a convalent bond.
Simple molecular substance
Low mp/bp
insulator
Name the structure and essential properties of a metallic bond
Giant lattice
High mp/bp
Conductor
What happens when halogens (group 7) react with metals?
Form ionic compounds
Why is it harder for halogens lower down the group to bond?
Atoms have more electron shells
The extra electron is further from the nucleus
So its attraction to the nucleus is weaker
(Harder for the atom to pull in an extra electron.)
Chlorine test
Damp blue litmus paper → turns white
As you go down in groups halogens get ……. …………..
As you go down in groups noble gases get ……. …………
Less reactive
More reactive
How to calculate RFM?
By adding the relative atomic masses (RAMs) of the atoms or ions
How to find percentage by mass of an element in a compound?
(Mass of element/RFM)x100
equation for moles
mass/RFM
table to calculate moles:
Element 1 Element 2
Mass:
RFM:
Moles:
Ratio:
How to calculate mole ratio in a formula?
Only look at big numbers: eg
2Na+S
If you were asked to find the mole ratio of Na to S, it would be 2:1 respectivly
Describe a metallic structure
A sea of delocalised electrons
A lattice of positive metal ions
How can metals conduct electricity?
Delocalised electrons can pass through the lattice
Define metallic bonding
The electrostatic attraction between the positive metal ions and the negative delcalised electrons.
