Chemistry 4 - Analysis and the Earth's resources (C12 - C15 Not chronological) Flashcards Preview

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Flashcards in Chemistry 4 - Analysis and the Earth's resources (C12 - C15 Not chronological) Deck (50)
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1

What formed the Earth's early atmosphere?

Volcanic activity

2

What was the most abundant gas in the earth's early atmosphere?

Carbon Dioxide.

3

What changed the amount of Carbon dioxide and increased the amount of Oxygen?

The evolution of green, photosynthetic plants.

4

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

5

What is the Anode?

The positive electrode

6

What is the Cathode?

The negative electrode

7

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.

8

What can be used to identify pure substances?

The fact that they each have a specific boiling and melting point.

9

What can melting and boiling point data be used for in pure substances?

Identifying and distinguishing them.

10

What are formulations?

Useful mixtures made up in different proportions.

11

What can scientist use to analyse unknown substances in solution?

Paper chromatography.

12

What is an Rf value?

A retention factor, it can be measured and matched against databases to identify specific substances.

13

What is the equation for an Rf value?

Rf = distance moved by substance / distance moved by solvent.

14

What does hydrogen gas do when you apply a lighted splint?

Burns rapidly with a pop.

15

What does oxygen do to a glowing splint?

Relights it.

16

What does Carbon dioxide gas do to limewater?

Turns it milky

17

What does chlorine gas do to damp blue litmus paper?

Turns it white.

18

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.

19

How can you identify carbonates?

By adding dilute ACID, which produces CARBON DIOXIDE GAS. The gas turns limewater milky.

20

What is a carbonate?

A compound containing carbonate ions (-2 charge)

21

What is a halide ion?

A halogen atom bearing a negative charge.

22

How is the presence of halides identified?

Adding NITRIC ACID to the solution, then SILVER NITRATE SOLUTION. This produces a precipitate of silver halide.

23

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

24

Name an instrumental method of analysing chemical substances.

Flame emission spectroscopy

25

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.

26

Name 3 renewable sources of energy.

Biofuels, wind energy, hydroelectricity

27

Name 3 non-renewable sources of energy.

Crude oil, uranium and natural gas

28

What is potable water?

Water that is safe to drink

29

Name 3 ways that water can be made fit to drink specifically by sterilising it.

- Adding chlorine
- Adding ozone
- Passing UV light through

30

Why is water rarely purified by distillation?

Expense due to energy requirement.