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Francisca > Chemistry > Flashcards

Chemistry Flashcards

1
Q

What is the definition of an ionic bond?

A

The ionic bond is the electrostatic attraction between the negative non-metal ion and the positive metal ion.

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2
Q

Describe the structure of ionic compounds.

A

An ionic compound is a giant lattice, with the forces of the ionic bonds going in all directions.

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3
Q

What are the key characteristics of ionic compounds.

A

High BP/MP because of the large amounts of energy needed to break the many strong bonds.

Ionic compounds can only conduct if molten or dissolved as in these forms the charged ions are able to move and carry current.

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4
Q

What is the definition of a covalent bond?

A

The electrostatic attraction between the negative shared pair of electrons and the positive nuclei.

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5
Q

What are the key characteristics of simple covalent molecules?

A

Low MP/BP because little energy is needed to overcome the weak intermolecular forces between molecules when melting or boiling.

The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points. (This is how fractional distillation of crude oil works).

Cannot conduct as there are no charged particles free to move

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6
Q

Can covalent molecules conduct?

A

No, because there are no charged particles free to move.

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7
Q

Can giant covalent structures conduct?

A

Diamond cannot conduct.

Graphite and Fullerenes can conduct, because they have delocalised electrons that are free to move and carry current/heat.

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8
Q

Do covalent molecules have high or low melting/boiling points?

A

Low MP/BP

Little energy is needed to overcome the weak intermolecular forces between molecules when melting or boiling.

The strength of the intermolecular forces depends on the size of the molecule. The bigger the molecule, the stronger the intermolecular forces, and the higher the MP/BP. This is why alkanes of different sizes boiling at different points so they are separated by fractional distillation. Larger alkanes = Stronger IMF = Higher BP.

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9
Q

Describe the structure of diamond, and how this results in its characteristics.

A

Giant covalent structure

Carbon atoms only

Each Carbon bonds to 4 other Carbons

No delocalised electrons - cannot conduct

Tetrahedral structure with many strong covalent bonds

Strong and rigid

High MP/BP

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10
Q

Describe the structure of graphite, and how this results in its characteristics.

A

Giant covalent structure

Carbon atoms only

Each Carbon bonds to 3 other Carbons

Forms layers of hexagons

1x delocalised electron per Carbon atom because each Carbon only bonds with 3 other Carbons, leaving one electron unpaired. These electrons are free to move and carry charge/current within the layer. Thus, graphite can conduct

Weak intermolecular forces between the layers so the layers can slide over each other. Therefore, Graphite is soft and slippery

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11
Q

Describe the structure of fullerenes, and how this results in its characteristics.

A

Carbon atoms only

Each Carbon bonds to 3 other Carbons forming hollow spheres

Delocalised electrons free to move within the sphere so it can conduct

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12
Q

What is the definition of a metallic bond?

A

The electrostatic attraction between the negative sea of delocalised electrons and the positive metal ions.

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13
Q

Describe the structure of metals.

A

Metals consist of giant structures of atoms arranged in a regular pattern. The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure.

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14
Q

Describe the characteristic properties of metals.

A

Metals are good conductors of electricity and heat because the delocalised electrons in the metal can move throughout the metal and carry electrical charge.

Metals have a higher MP and BP due to the metallic bonds being strong and needing a lot of energy to be overcome.

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15
Q

What are alloys?

A

In pure metals, atoms are arranged in layers, which allows metals to be bent and shaped. This is because the regular layers can slide over each other.

These pure metals are too soft for many uses and so are mixed with other metals making alloys, which are harder.

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16
Q

Explain the process of fractional distillation of crude oil.

A

Fractional distillation is used to separate the alkanes according to their size.

The smaller molecules have a lower boiling point so they travel further up the chamber and are distilled higher up. The larger molecules have a lower boiling point so they condense closer to the bottom of the chamber.

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17
Q

Name and describe he use of each of the fractions of crude oil’s fractional distillation products.

A
19
Q

Describe the differences between the alkanes distilled at the top versus at the bottom of the chamber.

A

As you go up the chamber, the alkanes are…

  • Easier to ignite
  • Flow more easily
  • Are more volatile (this means they evaporate more easily)
  • Have a lower boiling point
20
Q

What is the difference between an alkane and an alkene?

A

Alkanes and alkenes are both hydrocarbons.

Alkanes have no double bonds, whereas alkenes have at least one double C=C bond.

This means alkanes are saturated whereas alkenes are unsaturated.

21
Q

What are the two types of cracking and how do they differ?

A

Catalytic cracking

  • Uses a catalyst called silica or alumina
  • The temperature is 600 to 700 degrees Celsius

Steam cracking

  • Mix with steam
  • The temperature is 800 degrees Celsius

Remember: Cracking breaks larger alkenes into smaller, more useful alkanes and alkenes

22
Q

How do alkenes react with halogens?

A

It is an addition reaction.

Both atoms of the halogen attach - so there’s only one product, the halogenoalkane

Ethene + Bromine → Dibromoethane

23
Q

How do alkanes react with halogens?

A

Requires the presence of UV light

Substitution reaction: Replacing a H with the Halogen

Product includes Hydrogen-Halogen

25
Q

What is the chemical test used to distinguish between alkanes and alkenes?

A

Add bromine water, which is orange brown, to the test liquid.

If the colour of the mixture stays orange brown, it was an alkane - it’s not reacting.

If the colour of the mixture becomes colourless, it was an alkene.

28
Q

Describe the difference between Lithium, Sodium and Potassium in their reactions with water.

A
29
Q

How does the BP and MP of Noble Gases change as you go down the group?

A

BP and MP increase as you go down the group as the RAM (relative atomic mass) gets bigger so more energy is needed to overcome the forces of attraction between the atoms.

30
Q

Why are group 0 elements unreactive?

A

Full outer shell - do not need to gain or lose electrons.

31
Q

Describe the reaction between an alkali metal and chlorine.

A
32
Q

What do alkali metals have in common?

A

Soft metals

First 3 are less dense than water - this means they float on water

They all have one electron on the outer shell

Alkali metals = Group 1, lose one electron when they react, called alkali metals as they form hydroxides when react with water.

33
Q

Describe the word equation for the reaction between an alkali metal and water.

A

G1 Metal + Water —> Metal Hydroxide + Hydrogen

35
Q

Write the word equation for the reaction between an alkali metal and oxygen.

A

G1 Metal + Oxygen –> G1 Metal Oxide

36
Q

What colour are group1 metal oxides?

A

White solids

38
Q

What happens when you dissolve chlorides in water?

A

They form colourless solutions.

39
Q

Describe the trends that occur as you go down group 1.

A

As you go down group 1…

  • Density increases
  • MP and BP decreases - as you go down, the ions get larger, which means the attraction between the nucleus and outer electron is weaker - the electrostatic forces get weaker - so less energy is needed to overcome the attraction so MP/BP gets lower
  • Reactivity increases as you go down the group because it is easier to lose the outer electron. This is because the attraction between the nucleus and outer electron is weaker. The attraction is weaker because as you go down the group the distance from the nucleus to the outer electron increases and there are more shells in-between the nucleus and outer electron, so the shielding effect increases.
40
Q

What do chlorides look like as solids?

A

White solids.

41
Q

What do all halogens have in common?

A

7 electrons in the outer shell

Halogens form diatomic molecules e.g. Cl2, I2, Br2

A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt. These are called displacement reactions.

42
Q

How does boiling and melting point change as you go down Group 7?

A

As you go down the group, the size of the atoms and therefore the size of the molecules get bigger.

The bigger the molecules, the stronger the intermolecular forces.

This means more energy is needed to overcome them, hence BP and MP increases.

43
Q

How does reactivity change as you go down Group 7?

A

Reactivity decreases as you go down the group because…

  1. As you go down the group, the atoms have more shells
  2. This means the distance between the nucleus and the outer electron increases
  3. This also means that there are more shells in-between the nucleus and outer electron, so the shielding effect increases
  4. Therefore the electrostatic attraction between the outer electron and the nucleus is weaker
  5. This means it is more difficult to gain the outer electron, making it less reactive.
44
Q

What does chlorine, bromine and iodine look like?

A

Chlorine = green gas

Bromine = red-brown liquid

Iodine = grey-black solid

As you go down the group, the colour gets darker and the MP increases so it goes gas, liquid, solid.

45
Q

What do chlorides look like?

A

Chlorine is a green gas.

46
Q

What happens when I react Bromine with Potassium Iodide?

A

The bromine displaces the iodine, to get Iodine and Potassium Bromide

The brown bromine liquid would disappear. A black solid would appear.

47
Q

What are the differences between transition metals and alkali metals?

A
  • All group 1 metals form ions with a +1 charge but the transition metals can form ions with variable charges
    • E.g. Iron can form Fe(II) or Fe(III)
  • Transition metals are much harder, stronger and denser than the group 1 metals, which are very soft and light
  • Transition have much higher melting points e.g. titanium melts at 1,688 ºC whereas potassium melts at only 63.5 ºC, not far off the average cup of tea!
  • Transition metals are much less reactive than the group 1 metals
  • Transition metals react very slowly or do not react with water, oxygen and halogens whereas the alkali metals do.
    • A group 1 metal will tarnish in the presence of oxygen as a metal oxide is formed.
    • Iron on the other hand can take several weeks to react with oxygen to form iron oxide (rust) and requires the presence of water.
48
Q

What is one of the main uses of transition metals?

A

Transition metals are very useful as catalysts.

Francisca (2 decks)

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