past papers

Question 1

what is a fraction?

Answer 1

a group of hydrocarbons with similar boiling points

Question 2

why does CO2 absorb IR?

Answer 2

C=O bonds vibrate at the same frequency as IR

Question 3

why is aqueous ethanol a suitable solvent when heating coconut oil with KOH?

Answer 3

allow to dissolve both oil and KOH

Question 4

way to improve accuracy of experiment to determine enthalpy value of combustion?

Answer 4

use a wind shield

Question 5

why do chemists aim to design production methods with fewer steps?

Answer 5

less energy used

Question 6

why are reactants added to excess NaHCO3?

Answer 6

to neutralise the acid and stop the reaction

Question 7

why does a graph w a constant gradient show 0 order?

Answer 7

ror doesnt change as conc changes

Question 8

observations of sodium heated in oxyegn

Answer 8

yellow flame
white solid

Question 9

how do you determine melting point of a sample?

Answer 9

using melting point apparatus
heat slowly

Question 10

why does cyclohexene have a shorter retention time than cyclohexanol in column chromatography?

Answer 10

cyclohexene is less polar than cyclohexanol
cyclohexene has greater affinity for the mobile phase

I DONT THINK THIS IS RIGHT

Question 11

example of a change to decrease percentage uncertainty in the use of the same thermometer

Answer 11

increase magnitude of temp change by increasing conc of acid/ alkali