Buffers, Carbon, Nitrogen and Phosphorous Flashcards
What are the 4 bulk elements?
Carbon, nitrogen, hydrogen and phosphorous
Where is carbon found?
- atmosphere - present as co2
- in biomolecules - carbohydrates, proteins and DNA
- geosphere - carbonate minerals and in sediments
How does the oxidation state of carbon change through the biogeochemical cycle?
oxidation state changes from -4 to +4
What is CO and what is it a product of?
- an odorless and colorless gas
- neutral oxide
- products of incomplete combustion of fossil fuels
Describe the structure of Carbon monoxide
Functions as a ligand for Fe in myoglobin and Hb
Co2 and water
produces carbonic acid - H2CO3
What is Henry’s law?
amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the solution
What happens to gas solubility as pressure increases?
• as pressure increases, gas solubility also increases
How do you determine the solubility of a gas from KH value?
the larger the kH value, the more soluble the gas
How do the Ka values of polyprotic acids differ and why?
- Ka1 is much bigger which is typical of polyprotic acids
• this occurs because once a proton is lost. it gets harder and harder to lose protons
• ie. the greater the negative charge on the acid, the heart it is to REMOVE H+
Describe what happens in the carbon cycle (simplified)
- CO2 in the atmosphere is dissolved in the ocean
- Ocean life, when they die, end up as sediments (CaCO3, MgCO3)
- these sediments are burnt and used as duel
- burning of fuel releases CO2 into the atmosphere
What is a buffer solution?
One that resists a chnage in pH when either OH- ions or H+ ions are added
• prevents large changes in pH
e.g. blood, the sea
How can a buffer solution be made?
Mixing a weak acid with its conjugate base
What makes a good buffer?
once that has close to equal proportions of the acid and its conjugate base
What does the lewis structure allow us to predict?
• allows us to make predictions about shape
• make predictions about reactivity
- ie. will a given molecule be able to act as a ligand and bind to a transition metal
How do you calculate the formal charge?
Number of valence electrons in the atom - (non bonding electrons + 1/2 bonding electrons)
What elements are the exceptions to the octet rule?
- octet can be exceeded for elements in the third period and beyond
- elements with and odd atomic number (ie. N)
What is a radical?
- species that contain single unpaired electrons
- often very reactive
- typically contain an odd number of electrons
What are the steps to drawing a lewis structure?
- count the total no. of valence electrons
- draw the atoms and give everything a single bond
- give the outer atoms an octet
- put remaining valence electrons in the central atom
- turn lone pairs into double bonds to give every atom an octet
- assign formal charges
Ozone shape and function
- v-shaped
- powerful oxidant
- role in the upper atmosphere in UV absorption is critical to life on earth
- screens out UV radiation which damages DNA
The oxygen cycle
Respiration - reduction of O2
Photosynthesis - involved oxidation of H2O (this is the source of all oxygen on the planet)
What is superoxide?
- superoxide ion can damage cells and is involved in many disease states
- also causes ageing
How are the effects of superoxide ions minimised?
- Superoxide Dismutase (SOD) is abundant in aerobic organisms
- its task is to destroy superoxide ions (Radical species) and hence protect against radical damage
What is the oxidation state of Sulfur?
-2
SO2 and water
SO2 dissolves in water to produce the weak diprotic acid H2SO4