chem very vital mistakes

what must you be doing for all qs in exam

→ write down what they are asking me

→ reread once done in case missed

→ move on and flag if tough. 

efficiency formula

usable energy = percent efficiency x total energy.

criteria for concentration time graph

1. change is drawn

2. ratio of change from eq shift is shown

3. equilibrium established exactly at the point, AND IT IS SMOOTHLY CONNECTED

percentage atom economy WHAT ARE THE STEPS TO DO

1. write this generalised→ Mr (desired product)/ Mr (all reactants)

2. write this SPECIFIC AND CHECK IF ALL DESIRED PRODUCT AND REACTANTS CORRECT. Mr (formula desired product) / Mr (formula reactant 1) + Mr (formula reactant 2etc)

DON”T RELY ON METHOD, for fats/triglyceride formula,

Triglyceride=(FA1​+FA2​+FA3​ OR IF SAME FATTY ACID X 3)+C3​H2​.

respiration formula

C6H12O6 (aq) + 6 O 2 (g) —> 6 CO2 (g) + 6 H2O (l)

ENSURE YOU HAVE RIGHT CHEMICALS AND RIGHT COEFFICIENTS

mass of substance when fully combusted from energy and energy/mass

total energy (J, MJ / energy/mass (e.g J/g, MJ/tonne, J/kg)

whenever there is a dilution and a calibration curve we have to find the concentration of the unknown solution of, what must we do in steps?

1. read concentration off the graph using peak area

2. extrapolate back to the original, undiluted value which you diluted from so you could fit on the calibration curve.

3. Do this by multiplying the concentration by how much it was diluted.

does voltage decrease in a fuel cell? why or why not?

No, not expected because continuous flow of reactants.

give me the response if the wrong optical isomer was used instead of the correct substrate.
Use example of proline amino acid, and lactose/substrate (carbo), lactase, (enzyme),

must identify that the optical isomer would alter the primary structure of the enzyme (wrong conformation) and cause the active site of the enzyme (name enzyme) to change shape.

With a changed active site in the name enzyme, the specify substrate would then no longer have the correct conformation/shape to match. Hence the lactose (thing)  would not be as effectively happened to (digested. etc.. .

in an exothermic reaction, how would the incomplete combustion differ from the complete combustion with energy profile diagram? why?

The first mark was awarded for recognising that the products of incomplete combustion needed to have a higher energy than shown for the complete combustion (but still below the reactants).

The second mark was awarded when the student identified this as being due to the incomplete oxidation of the reactants, which is the reason for less energy being released.

photosynthesis formula

6 CO2 (g) + 6 H2O (l) —> C6H12O6 (aq) + 6 O 2 (g)

ENSURE YOU HAVE RIGHT CHEMICALS AND RIGHT COEFFICIENTS

methane sources

organic waste matter / biomass / coal seam gas / cattle / biogas / anaerobic respiration / fossil fuels / natural gas / fracking.

HOW IS polarity of electrodes establish during recharge to allow recharge to occur? does electrode polarity change? what happens at what? what does the external power source do? what does the reversal of processes help with?

MEMORISE BOLDED PARTS MAINLY

The first mark was awarded for the recognition that the electrode polarity does not change when the system is changed from discharge to recharge.


The relative reductive and oxidative strength of the chemicals present in the galvanic cell is what determines the polarity, and this is fixed for both the discharge and recharge processes.

The second mark was awarded for the recognition that the external power source causes the process to change at each electrode. This means that during the recharge the positive electrode becomes the anode and oxidation occurs here. This reversal of processes means that the original chemicals can be re-formed and hence the cell is recharged.

Why different frequencies of IR, can be absorbed by the same molecule as shown above (random IR graph)

different bonds, or the functional groups, are what is causing the absorption of different frequencies of infrared radiation.

accuracy improvements for can in calorimetry for the true value? why do that improvement?

Accuracy improvements What is the true value? The true energy content? If put a lid on it, be careful as that may result in partial oxidation. ‘An improvement could be to ensure better insulation was used on the outside container. This would allow for more energy to be effectively transferred to the water and thus allow for a more accurate ΔT and hence a final energy content that would be closer to the true value.’ ‘An improvement could be to conduct multiple trials so that outliers could be removed from the data set. This would allow for a final energy content to be calculated that would be closer to the true value.’

Green hydrogen, 3 key things, sourcing, process and a key method typically making it

Generated via renewable sustainable sources also all in the process would have to be renewable, generated via electrolysis using sustainable energy sources

PEM -electrolysis of water to hydrogen gas

Polymer Electrolyte membranes, prevent the mixing of products (H2 and O2 which will spontaneously react)

-electrodes coated with catalyst

-gas diffusion layers help distribute reactant gases equally. 

→ PEM, is selectively permeable to H+ ions but not to other ions/electrons, prevents passage of water/hydrogen and oxygen molecules.

artificial photosynthesis- -electrolysis of water to hydrogen gas

→ human made materias capture sunlight to split hydrogen and oxygen

→ catalyticaly covered nanomaterials which also increase reaction rate.

when the size of the equilibrium constant is <10-4, when it is between 10-4, and 10^4, when it is 10^4

→ equilibrium constant is small if less than 10-4, and big if greater than 10^4

challenges with green hydrogen

energy requirements → need significant energy input. 
infrastructure→ lacking current infrastrucutre ot support production, storage and transport of hydrogen. 
cost → stilll costly compared to traditional fuel sources, pressures to contain during travel.
water requirements - lots of water use, not viable where water is needed, or/and scarce

accurately determine concentration how to do (in titration)

→ repeat titration using a diff standard solution

how can the peak splitting and relative peak be described

• There are x number (x = relative peak area given in table most likely., or graph if need be,) equivalent hydrogen atoms at that chemical shift.

•   There are y equivalent hydrogen atoms on adjacent carbon atoms.

adding inert gas to equilibrium effects

0. No change

   There are more collisions due to added particles but not more successful collisions since collisions involving inert gas particles do not affect equilibrium. Inert gas molecules are not part of the equilibrium reaction.

example (NOT NECESSARILY ALWAYS) KOH purpose in cells

electrolyte,
source of OH- ions

2018 NHT hard q, if they say chlorine faint smell when it is concentrated like 4M or something and there is both water and chlorine in the solution, what gas is produced?

IT IS NOT CHLORINE COMPELTELY, i know a trip up, but because faint smell, that menas that it is not completely that means it is not completely oxidised and O2 is produced instead.

tertiary structure on enzyme, on active site? substrate purpose and how bind? which models can it occur in?

3d teritarty structure of enzyems is maintiained by R group interactions, SUCH AS H bonds, disperson forces, dipole dipole forces, ionic bonds and more gives the enzyme its shape and specific active site conformation. 
Substrate is complementary in shape to the specific active site faciliating specifity and the reaction.
When the substrate binds bonds such as h bonds, disperson forces, dipole dipole forces and ionic bonds are formed. 
This can occur in induced fit model where (active site conformation is flexible) or lock and key model (no change in acitve site)

temperature increase on the activity and rate of reaction of the enzyme

Increase in temeprature increases kinetic energy, disrupts the H bonds, dipole dipole bonds, ionic bonds and more bonds in the 2ndary, 3tiary, and quartenary strucutres but no the primary strucutere held together by covalent bonding. 

3D teriary structure changes enzyme shape and strucutre unfolding the prtein and denaturing it, rendering the acitve site uncomplementary unable to bind wirh specific substrate.

thus cant catalyse further, reducing enzymatic rate of reactuon and reducing enzyme activity

and decrease on the activity and rate of reaction of the enzyme

Decrease in temperature decreases kinetic energy decreases enzyme substrate collisions

frequency of cataluytic collisions reduces
structure unaffected

no change in active site, but enzymatic rate of reaction decreases.

why different frequencies of IR can be absorbed by the same molecule

Diff bonds have different bond strengths and different IR frequencies
Stronger bonds needing more energy thus a higher frequency to be absorbed by the same molecule to break.
Heavier masses vibrate at lower frequencies

solubility q example (imagine vitamin e is a big molecule with 1 ether link and long other part) why vitamin E soluble in coconut oil

Both vitamin E and coconut oil are non polar compounds and contain primarily non polar groups and chains,
Vitamin E would dissolve in the coconut oil as it forms dispersion forces

why is a big coconut oil compound be not practical for a fuel cell with aqueous KOH electrolyte

→ non polar, not soluble in aquueous electrolyte
→ very long as very viscous, clog, and not very efficient to run

explain why something has optical isomers

because it has a chiral carbon surrounded by 4 different groups, this forms optical isomers which are non superimposable mirror images of each other and enantiomers.,

why must we be careful for enzyme optical isomer questions?

must be careful whether they ask us if an optical isomer is in an enzyme or the substrate.

if optical isomer in enzyme, than any different substrate forms different interactions and thus changes active site deforming it so it is not complementary to the substrate anymore.

If optical isomer in substrate, it is non superimposable and the lock and key model demands it be complementary

do chiral centres guarantee optical isomerism?

only if there is an odd number

enantiomers properties chemical and physical

same chemical, as diff 3D shaoe, interact diff ways,

same physical, as same molecular formula, and same IMFs

R group residues interacting determine what?

→ 3D shape,

Mixture of soybean plant extract, what distillation Method and why?

How does secondary hierarchy structure work

Secondary hierarchal structure works by:
Exists in a single polypeptide chain, existing between the polar C=O group of a peptide linkage

and a a polar N-H group on another peptide link.
They can be directly between opposite ends to form a spiral alpha helices, parallel ends to form beta pleated sheets or irregularly in combination to form random coils. 

What does the prescence of disulphides bridges mean the amino acid must be? What does that mean for the proteins properties?

How something binding to an enzyme restricts its function?

What determines the teriary sttructure?
How does change in ph and temp differ in denaturation,

Consider process,

Consider high and low ph and temperature and it’s effects on enzyme

Consider effects on hierarchal levels

Intermolecular bonding formed between inhibitor and enzyme? (Catopril and ACE enzyme)

why two half cells are separated in fuel cells

->because they need to generate electrical energy, second reason is electrons need to travel through the wires and load, oxidation and reduction would occur together and they would not move through the external circuit.

what causes the movement of ions across a fuel cell?, (example H+ ions),

the electrodes, => talk about how as electrons leave from an electrode (anode/oxidation/loss of electrons) it becomes more positively charged, and when electrons are gained by a cathode/reduction/gain of electrons, it becomes negatively charged.

The ion which is being moved, for example H+ is repelled by the like charge and attracted to the opposite charge,

how can chemical products of metabolism make large biomolecules?

→ metabolism split up into chemical products of monomers (amino acids, glucose)

→ can be used by body in condensation reaction to form large biomolecules (proteins, glycogen)

advantage of using something which is a part/reactant of the electrolytic cell (electrode etc) instead of an inert electrode like platinum?

acts as a source of that ion, helps make sure the concentration is the same.

(mentioning cost is worst case, with platinum, always try finding more salient ones from the context of the question.

IN Q W A PPM AND A PEAK SPLITTING e.g explain w reference to structure of chemical X, why there is a y splitting pattern around n ppm in the H NMR spectrum

, FOLLOW THESE TWO STEPS => what group caused this specific ppm? ==> why are the number of peaks that?