Chemistry 4 - Analysis and the Earth's resources (C12 - C15 Not chronological) Flashcards
What formed the Earth’s early atmosphere?
Volcanic activity
What was the most abundant gas in the earth’s early atmosphere?
Carbon Dioxide.
What changed the amount of Carbon dioxide and increased the amount of Oxygen?
The evolution of green, photosynthetic plants.
What are the stages of Sewage Treatment?
- Passed through pumping station
- Screened
- Primary sedimentation
- Biological treatment
- Secondary sedimentation
- Water is disinfected/sterilised at this point
- Added to river
What is the Anode?
The positive electrode
What is the Cathode?
The negative electrode
What is the difference between a pure and impure substance?
A pure substance can be a compound, but it must contain only one substance. An impure substance is a mixture of two or more different elements or compounds.
What can be used to identify pure substances?
The fact that they each have a specific boiling and melting point.
What can melting and boiling point data be used for in pure substances?
Identifying and distinguishing them.
What are formulations?
Useful mixtures made up in different proportions.
What can scientist use to analyse unknown substances in solution?
Paper chromatography.
What is an Rf value?
A retention factor, it can be measured and matched against databases to identify specific substances.
What is the equation for an Rf value?
Rf = distance moved by substance / distance moved by solvent.
What does hydrogen gas do when you apply a lighted splint?
Burns rapidly with a pop.
What does oxygen do to a glowing splint?
Relights it.
What does Carbon dioxide gas do to limewater?
Turns it milky
What does chlorine gas do to damp blue litmus paper?
Turns it white.
Name two ways that some positive ions (Cation) can be identified.
- Some metal ions (including Group 1 and 2 cations) can be identified in their compounds using FLAME TESTS.
- SODIUM HYDROXIDE solution can be used to identify metal ions that form insoluble hydroxides in precipitation reactions.
How can you identify carbonates?
By adding dilute ACID, which produces CARBON DIOXIDE GAS. The gas turns limewater milky.
What is a carbonate?
A compound containing carbonate ions (-2 charge)
What is a halide ion?
A halogen atom bearing a negative charge.
How is the presence of halides identified?
Adding NITRIC ACID to the solution, then SILVER NITRATE SOLUTION. This produces a precipitate of silver halide.
When a halide is identified resulting in the production of a silver nitrate precipitate, what colour will this precipitate be in the presence of chloride, bromide or iodide ions respectively?
If chloride ions are present (Cl-) - White
If bromide ions are present (Br-) - Cream
If iodide ions are present (I-) - Yellow
Name an instrumental method of analysing chemical substances.
Flame emission spectroscopy
What does flame emission spectroscopy identify?
Which metal ions are present from their characteristic line spectra, and also the concentration of the metal ions in a solution.
Name 3 renewable sources of energy.
Biofuels, wind energy, hydroelectricity
Name 3 non-renewable sources of energy.
Crude oil, uranium and natural gas
What is potable water?
Water that is safe to drink
Name 3 ways that water can be made fit to drink specifically by sterilising it.
- Adding chlorine
- Adding ozone
- Passing UV light through
Why is water rarely purified by distillation?
Expense due to energy requirement.
Name and explain a desalination method that does not include sterilisation or distillation.
Reverse osmosis uses membranes to separate dissolved salts from salty water.
How is copper extracted from ore most commonly?
Smelting.
How can copper be extracted from solutions of copper compounds?
Electrolysis.
What is a Life Cycle Assessment? (LCA)
An assessment carried out to identify environmental impact of products, processes or services.
How can the 4 stages of an LCA be summarised?
Raw material extraction - > Manufacture - > Use/Reuse/Maintenance - > Recycle/Waste management
What two things are needed to cause iron to oxidise (Rust)
Oxygen and Water
What can prevent iron from rusting?
Creating a barrier between the air/water and the iron.
What is sacrificial protection?
When rusting is prevented by attaching the iron to a more reactive metal.
What are alloys?
Combinations of metals that are harder than pure metals.
Why are alloys harder than pure metals?
Because the regular layers in a pure metal are distorted by differently sized atoms in an alloy.
What are polymers?
A substance made up of very large molecules made up of many repeating units.
What are monomers?
Small reactive molecules that react together to form large molecules.
What affects the properties of a polymer? Two things.
- The monomers that produces the polymer.
- Changing reaction conditions
What are thermosoftening polymers?
Polymers that will soften or melt easily when heated because their intermolecular forces are relatively weak.
What are thermosetting polymers?
Polymers that do not melt when heated because their covalent bonds are strong forming cross links between polymer chains.
What is soda glass made of?
Sand, limestone, and sodium carbonate
What is borosilicate glass made of?
Sand and boron trioxide
What are the conditions under which the Haber process is most frequently executed and why?
450 degrees celsius and 200 atmospheres using an iron catalyst. These are the most efficient conditions economically for the process.
Why are higher pressures not used in the Haber process?
Because despite the higher ammonia yield, it is too expensive.
Why are lower temperatures not used in the haber process despite yielding more ammonia?
Because this would make the process less efficient due to the slower speed.
