Exam mistakes

Question 1

what does de-oxygenated water mean?

Answer 1

still water molecules but with no extra oxygen gas dissolved in solution

Question 2

what does a titration curve look like no matter what species is being used?

Answer 2

always a sharp titration curve (but maybe translated up or down). HOWEVER, with a weak acid and weak base the curve has a gradient and is not just vertical.

Question 3

what is the relationship between volume and concentration?

Answer 3

It is direct. e.g: halving the volume equals doubling the concentration

Question 4

how can we calculate avogradros constant?

Answer 4

(no. of electrons) / (mol of electrons)

no. of electrons calculated by charge of cell (in coulombs) divided by charge of 1 electron.

Question 5

what molecules are produced through oxidative rancidity?

Answer 5

aldehydes= bad smell/taste

Question 6

why are electrolytes with a number of different ions sometimes preferred?

Answer 6

as mixtures have lower melting points than pure substances.

Question 7

bubbles of reactant gases increases the rate how?

Answer 7

by an increased surface area.

Question 8

how to tel from a line diagram the structure of a protein

Answer 8

if there are at least two bold lines (representing individual chains) then the structure is quaternary as this is different proteins bonding together.

Question 9

for zwitterions where can protons be accepted or donated?

Answer 9

at the amino, carboxyl on side chains or off the alpha carbons.

Question 10

in column chromatography what is peak area related to?

Answer 10

peak area has a direct correlation with concentration of substance.

Question 11

what are the formulas for energy?

Answer 11

E(in coulombs)=It
E(joules)=VIt
E(joules)=QV

Question 12

what is the main advantage of using a hot plate as oppose to a bunsen burner?

Answer 12

flammable substances are not exposed to a flame on a hot plate and therefore cannot light on fire.

Question 13

Why can methyl esters absorb moisture form the atmosphere?

Answer 13

The polar C=O bond in the ester can form dipole-dipole intermolecular bonding with polar water molecules and therefore absorb moisture.

Question 14

what is the thiol functional group?

Answer 14

-SH

undergoes reduction to form disulphide bridges

Question 15

what does ascorbic acid (Vitamin C) do?

Answer 15

Is an anti-oxidant.

A strong reductant that prevents free radical formation.

Question 16

what are some common greenhouse gases?

Answer 16

CO2
CH4
H2O

Question 17

what are the energy transformations that occur in a typical power station

Answer 17

chemical –>
thermal –>
mechanical –>
electrical

Question 18

what foods are likely to give rapid increase in blood-sugar levels?

Answer 18

ones with lots of carbohydrates in them as carbs can be digested quickly and easily. starchy things e.g: baked potato.

Question 19

why must we add water to a volumetric flask last and not first?

Answer 19

If we added water first and then the other substance this may not give 250ml. Some substance are miscible with each other which could cause inaccurate results if not added in the correct order.