CHEMISTRY 2018

Question 1

why is it difficult to identify the metal ions from the colour of the flame?

Answer 1

flame colours can be masked by others. the colours can blend and you can only see one

Question 2

bromide or bromine ions

Answer 2

BROMIDE

Question 3

how is ethanol produced from a sugar solution

Answer 3

conditions must be anaerobic and warm. yeast must be added so fermentation can occur.

Question 4

alcahol + what = carboxylix acid

Answer 4

oxidising agent

Question 5

why would a formulation have a purple and foul smell

Answer 5

to deter consumption and drinkage

Question 6

how has the concentration of gasses in earths atmohsphere changed

Answer 6

changes
* carbon dioxide has decreased
* oxygen has increased
processes
* volcanic activity released water vapour
* the water vapour condensed to form oceans
* carbon dioxide dissolved in oceans
* carbonates produce sediments
* carbon locked up in sedimentary rocks
* algae and plants evolved / appeared
* algae / plants absorbed carbon dioxide
* by photosynthesis
* which also released oxygen
* carbon locked up in fossil fuels

Question 7

pressure for harber process

Answer 7

200 ATM

Question 8

why are scientests unsure about % of gas in early atmohsphere -

Answer 8

• limited evidence
• happened 4.6 billion years ago

Question 9

if colours are only soluble in ethanol why is it bad of water is used in the beaker

Answer 9

water used (as solvent)
or
water in beaker
(so) colours will not dissolve /
move

Question 10

Explain why the solution becomes cloudy ( sodium thiosulfate)

Answer 10

sulfur produced which is a solid precipitate

Question 11

Plan an investigation to show how the concentration of the sodium thiosulfate solution
affects the rate of the reaction with dilute hydrochloric acid.
Your plan should give valid results.

Answer 11

• measure (indicated) volume of sodium thiosulfate
• place sodium thiosulfate in (conical) flask
• measure (indicated) volume of hydrochloric acid
• place on cross or between light sensor
  or
  connect to a gas syringe
  or
  other suitable method for timing a change
• add hydrochloric acid to (conical) flask
• swirl
• start stopclock / stopwatch
• measure time for cross to become no longer visible
  or
  log light transmission over time
  or
  measure time for fixed volume of gas to be produced
• repeat and find mean
• repeat for different concentrations of sodium thiosulfate
  or change ratio of sodium thiosulfate volume : water volume
  control variables
• concentration of hydrochloric acid
• volume of hydrochloric acid
• (total) volume of sodium thiosulfate solution

Question 12

A mixture of poly(propene) and wool to make carpets is more sustainable than using
just poly(propene) or just wool.
Suggest why

Answer 12

• poly(propene) comes from a
  non-renewable source
• poly(propene) requires a lot
  of energy to make
• poly(propene) is not
  biodegradable
• a wool carpet needs
  replacing more often
• wool requires the use of
  large areas of land (which
  could be used to grow food
  crops

Question 13

Give one reason for having a maximum allowed percentage of unburned
hydrocarbons in exhaust fumes

Answer 13

any one from:
* (to reduce) health problems
* (to reduce) global dimming

Question 14

The higher pressure gives a greater yield of methanol and an increased rate of
reaction

Answer 14

(yield)
equilibrium position moves to
the product side
(because) fewer molecules /
moles / particles on product side
(rate)
more collisions per unit time
(because) more molecules /
particles per unit volume

Question 15

Suggest why a catalyst is used in this industrial process.
Do not give answers in terms of increasing the rate of reaction

Answer 15

less energy is needed

Question 16

when reffering to formulations

Answer 16

dont talk about combiing useful properties talk about them seperatley

Question 17

when talking about chromotograohy dont talk about pure

Answer 17

talk about how many colours they share if any, and