BMS1060 - Biochemsitry Wk1-2 Flashcards
(60 cards)
All atoms of a particular element all have the same number of _______.
What are isotopes?
protons
isotopes = atoms of the same elemt but a different number of neutrons.
Atomic weight =
number of protons + number of neutrons
(rarely a whole number - average of different isotopes)
What is the difference between intermolecular and intramolecular bonds?
INTERmolecular - act between molecules
INTRAmolecular - act within a molecule
Give two properties of compounds with ionic bonding.
High m.p and b.p and water soluble
Do covalent structures or ionic structures have a higher b.p and why?
Ionic structures: Stronger bonds
What is a dative bond?
A covalent bond between two atoms where one atom gives both of its electrons to the bond.
e.g. haem
What is electronegativity?
What do the values range from?
A measure of the tendency of an atom to attract a bonding pair of electrons.
0.7-4.0
Where in the periodic table are elements most electronegative and why?
As you go ALONG (–>) the period, more protons so greater positive charge - greater attraction of electrons.
As you go UP the group, less electron shielding so greater attraction of electrons.
What causes the bond in a molecule to be polar?
Differences between the atoms in electronegativity.
Electron distribution skewed towards the more electronegative element.
What are the 3 types of intermolecular bonds?
Van der Waals
Dipole-dipole interactions
Hydrogen bonding
Describe Van der Waals
Electrons move around by chance - uneven distribution of electrons.
This causes an instantaneous slight negative charge in one side of the atom.
Describe Dipole-Dipole interactions
Found in polar molecules - differences in electronegativity between atoms.
Electrons pulled more towards one atom, causing slight neg and sligh pos charges at either end of molecule/bond.
Describe hydrogen bonding.
Which bonds commonly have H-bonding?
Weak electrostatic attraction formed between polar molecules which occurs when an H atom binds to a lone pair of electrons on a highly electronegative atom.
O-H, F-H, N-H, Cl-H
1 mole of a subsance contains…
The same number of atoms as in 12g of pure carbon-12 (6.02x10^23)
What is the equation to work out the n.o of moles of a substance using mass and Mr?
n.o. of moles = mass (g) / formular weight
n = m / Mr
1L = ? dm^3
1L = 1 dm^3
What is the equation to work out the n.o of moles of a substance using concentration and volume?
n.o. of moles = concentration x volume
n = cv
What is Collision Theory?
The concept that reactant molecules must collide with sufficient energy and in the correct orientation to react.
What is Activation Energy?
What are the two types? Enthalpy change?
Ea = the energy needed to react two reactants together.
Exothermic - energy released - neg ΔH
Endothermic - energy consumed - pos ΔH
What happens in exothermic and endothermic reactions?
MEXO BENDO
Endothermic - energy consumed when bonds are broken (+ΔH)
Exothermic - energy released when bonds are formed (-ΔH)
What do catalysts do?
Lower activation energy - so a greater proportion of molecules can react.
In terms of the Maxwell Boltzmann Distribution, what happens to the % of molecules that react when temperature increases and decreases?
Temp increase - % of molecules with sufficient energy to react increases.
Temp decrease - % of molecules with sufficient energy to react decreases.
What determines the rate of a reaction?
(Maxwell Boltzmann Distribution)
The number of molecules with activation energy.
When is a reaction ‘feasible’?
When it is ‘energetically favourable’ at a certain temperature.
