CHEMISTRY Flashcards

Question

What are fullerenes?

Answer 1

Carbon that comes in the form of hollow shapes such as balls, tubes and cages. The Buckminsterfullerenes or buckyballs (named after American inventor and thinker, Buckminster Fuller) has the shape of a football - C(60) - tessellated with hexagonal and pentagonal shapes. Because they are very small and stable Fullerenes are used to deliver drugs into the body, as lubricants, as catalysts, and reinforcing materials (e.g., frames of tennis rackets) Buckyballs also turn darker when intense light is shone at them - good for safety glasses. For MORE on this see docbrown's pages: http://www.docbrown.info/page03/nanochem04.htm

Answer 2

1. Very large organic molecules (organic = based on carbon) 2. The constituent atoms are held together by strong covalent bonds Intermolecular forces between the molecular strands are also very strong. 3. Solid at room temperature. Extra info: Plastics are all polymers - bags, plastic bottles. E.g., Polythene is produced when lots of ethene molecules are joined together in an "addition polymerisation" reaction. DOWNSIDE: can fill up landfills, don't biodegrade easily, can cause a mess in our seas and oceans!

Answer 3

A metallic bond is the attraction between the positive ions and delocalised negatively charged electrons. Recall that electrons in metals flow freely around their atoms, because metals have a giant structure in which the electrons in the outer shell I'm not bound to anyone atom..

Answer 4

Metallic bonds are very strong. They have high melting and boiling points. This means they are useful for building and structure materials. They can conduct electricity they have good thermal properties metals. Also: malleable (easily bent/moulded) And: ductile (which means they can be stretched out as in wire).

Answer 5

And alloy is a mixture of two or more metals. They are used to strengthen or to provide different properties to the main metal. The added element disturbs the regular arrangement of the pure metal so that the atoms do not slide over one another so easily.. For example mixing iron with carbon creates steel.

Answer 6

The total mass of the products is equal to the total mass of the reactants. In other words what goes in must come out. This is why we use chemical equations to show that both sides must balance.

Answer 7

A half equation shows what happens to a reactant with a focus on its electrons. The key here is to count the number of missing electrons. E.g., if iron is put into copper (II) sulphate, the iron loses 2 electrons: Fe_(s) -\> Fe_(aq) ²⁺ + 2e^-.

Answer 8

The sum of all the relative atomic masses (A_r) E.g., C₂H₄0₂(vinegar!) A_r =\> C = 12, H = 1, O=16 C =\> 12 x2 = 24 H =\> 4 x 1 = 4 O =\> 16 x 2 = 32 THEREFORE M_r of vinegar C₂H₄0_{2 =} 60 [24+4+32]

Answer 9

Not all chemical reactions take place in closed systems. So some gas molecules may leave the open or **'non-closed' system** or react into it from the air. E.g., heating Mg _(s) draws O_2(g) from the air, so 2Mg (s) -\> 2Mg02(s) While when calcium carbonat is heated, it gives off CO₂. When the gases are 'caught' then the conservation of mass is secured.

Answer 10

amount in mols = mass in grammes / formula mass E.g., We have 88 grammes of CO₂. Formula mass of CO₂ is 44. No. of mols = 88/44 = 2

Answer 11

It is a standardised measure of the number of particles in a substance. The number of particles (atoms, ions, or molecules) is always 6.023 x 10²³. It is called Avagadro's constant after the man who counted them all. "Now we know how many moles it takes to fill the Albert Hall..." sung the Beatles in *Day in the Life*. Sort of :) Thankfully, the mass of one mol relates to the relative atomic mass of an element. E.g., C₁₂ has a mass of 12g which is one mol of carbon. O₁₆ has a mass of 16g, which is one mol of oxygen. CO₂ has a mass of 44g, which is one mol of carbon dioxide.

Answer 12

When one of the reactants is completely used up in a reaction, it stops the reaction from continuing - hence it is a *limiting* reaction.

Answer 13

Concentration = mass of a solute /volume of a solution [*solute* = that which is to be dissolved; it needs to be *soluble*; it then makes a *solution*] E.g., 2.00g solute (eg, salt) dissolved to form 1.00dm³ of solution (eg, water) the concentration would simply be 2 /1 = 2 g/dm³(salt water or brine) If 5.00g of solute dissolved to form 2.00dm³ of solution, the concentration would be 5/2 = 2.5g/dm³

Answer 14

Giant structures of ions Held together by strong forces of attraction \* high melting and boiling points \* do NOT conduct electricity when solid \* DO conduct when molten (ions are then free to move around - ions are charged particles!)

Answer 15

Giant covalent structures \* linked by strong covalent bonds \* high melting and boiling points E.g., diamonds (carbon allotrope) have \* rigid covalent LATTICE structure Each Carbon has four bonds No charged particles Does not conduct electricity silicon dioxide - lattice structure like a diamond GRAPHITE: high mp and bp carbons form 3 bonds layers are held together by weak intermolecular forces makes graphite soft and slippery conducts electricity

Answer 16

Polymers \* large molecules \* synthetic \* molecules are held together by strong covalent bonds \* solid at room temperature \* cheap and strong

Answer 17

Properties of metals \* metallic bonds make them really strong - useful for making structures \* electrons are delocalised \* good thermal and electrical conductors \* layers can slip over each other easily which makes metal malleable (bent and shaped) \* ductile - made into wires (duc- to lead) \* SOME METALS react with oxygen - RUST Others do not react so quickly and hence are good for carrying water (e.g., copper)

CHEMISTRY Flashcards

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