1.30 recall the charges of common ions in this specification

K +
Na +
Li +
H +

Mg 2+
Ca 2+

Al 3+

Cl-
Br-
I-
F-
OH-

NO3-

SO4 2-

CO3 2-

1.56 recall that one faraday represents one mole of electrons

One Faraday is 96500 coulombs. That is the amount of coulombs in one mole of electrons.

1.57 calculate the amounts of the products of the electrolysis of molten salts and aqueous solutions

One faraday is 96500 coulombs. It is also one mole of electrons.

If current of 0.2 Apms is passed through copper(ll) sulphate for tow hours, how much copper do you get?

• Write out the half equation

Cu2+ + 2e > Cu

• Work out coulombs of electrons flowing

Coulombs= current x time
Q= IT

time is 2x60x60 (times 60 makes minutes, times 60 again makes it seconds)

Q= 0.2 x 7200= 1440 coulombs

• Convert C into moles of electrons

Moles= C/Faraday

Mol= 1440/96500

Mol= 0.015

• Work out scale factor

Cu2+ + 2e > Cu

For every 2 moles of electrons, there will be one Cu

Sf= Moles of product/ moles of electrons

Sf= 1/2

Sf= a half

• Work out moles of product using Scale factor

so we do the moles of electrons times the scale factor

0.015x1/2= 0.0075 Moles of Cu

• Convert moles into mass

Moles x Mr

0.0075 x 63.5= 0.48g of copper

1.55 write ionic half-equations representing the reactions at the electrodes during electrolysis

At the positive electrode, electrons will be lost: to show this we write the lost electrons as products:
2Br- > Br2 + 2e-
Make sure the charges are equal on both sides: 1- > 1-.

At the negative electrode, electrons will be gained so we write them as reactants:
2H+ + 2e- > H2
And to make sure the charges are the same on both sides: 0 > 0.

1.54 describe experiments to investigate electrolysis, using inert electrodes, of aqueous solutions such as sodium chloride, copper(II) sulfate and dilute sulfuric acid and predict the products

Place inert electrodes (ones that wont react) into an aqueous solution.

At the positive electrode the negatively charged ion from the compound will form an atom. At the negative electrode the atom of the positive ion will form.

sodium chloride: Hydrogen at the negative; chlorine at the positive
copper(II) sulfate: copper at the negative; oxygen at the positive
dilute sulfuric acid: Hydrogen at the negative; oxygen at the positive

If the metal in the solution is more reactive then hydrogen, the hydrogen from the water will be a product, as the metal will bond with the oxygen.

Test the products using known methods: eg damp blue litmus paper turned red by chlorine.

1.53 describe experiments to investigate electrolysis, using inert electrodes, of molten salts such as lead(II) bromide and predict the products

Inert electrodes are ones that don't react with any other substances, but only play a role in the transfer of electrons.

To describe an experiment you need to be able to draw and label an electrolysis experiment. As an example:

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Lead bromide will make lead and bromine, you can use chemical tests to see is you got these products from electrolysis.

1.52 understand that electrolysis involves the formation of new substances when ionic compounds conduct electricity

In electrolysis ionic compounds conduct electricity. Positively charged ions move to one end, negatively to the other, these are then turned into atoms (by losing their charge) and so new substances are formed.

1.51 describe experiments to distinguish between electrolytes and nonelectrolytes

Set up an electric circuit with an LED and a break in the wire, put both ends of wire into a solution/molten substance. If the LED lights up then there is a current flowing, this will only be able to happen if the solution is conducting: so it must be an electrolyte. Conversely if the LED does not light up then there is no current flowing, and so the solution has not conducted electricity meaning it must be a nonelectrolyte.

1.50 understand why ionic compounds conduct electricity only when molten or in solution

When ionic compounds are molten or in solution, the positive and negative ions separate  this means that there are ions free to flow, and so they can conduct electricity.

1.49 understand why covalent compounds do not conduct electricity

In covalent compounds there are no electrons free to move, this means there can be no transfer of electricity through a covalent compound

1.48 understand that an electric current is a flow of electrons or ions

An electric current is a flow of electrons, although it can also be a flow of ions (as they have a charge.)

1.47 explain the electrical conductivity and malleability of a metal in terms of its structure and bonding.

Metals have delocalised electrons, electrons carry electricity; so because there are free electrons charge can pass easily through a metal.

The structure of a metal is with rows of atoms on top of one another, in pure metals as all the atoms will be the same size, the layers can slide easily over one another making them easy to bend.

1.46 understand that a metal can be described as a giant structure of positive ions surrounded by a sea of delocalised electrons

In a metal atoms come together into a lattice, the electrons become detached from their atoms- delocalised- making the atoms positive ions.

1.36 describe an ionic crystal as a giant three-dimensional lattice structure held together by the attraction between oppositely charged ions

An ionic crystal is a lattice of electrons in a 3D structure, the ions are alternate positive and negative and their opposing charges hold the structure together.

1.37 draw a diagram to represent the positions of the ions in a crystal of sodium chloride.

In a lattice structure with negative touching positive and visa versa.

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1.45 explain how the uses of diamond and graphite depend on their structures, limited to graphite as a lubricant and diamond in cutting.

In Graphite the atoms from layers, these layers can slide over each other, this makes it very slippery and so can be used as a lubricant.

Diamond is extremely hard because it has a many bonds in it, this means it is great for cutting as it can cut anything.

1.44 draw diagrams representing the positions of the atoms in diamond and graphite

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Carbon atoms in Graphite (left), are each bonded to three other atoms.

Diamond (right) is formed of carbon atoms each joined to four others.

1.43 explain the high melting and boiling points of substances with giant covalent structures in terms of the breaking of many strong covalent bonds

A giant covalent structure is one with many atoms bonded together. To melt or boil them you are not separating intermolecular bonds (between molecules), you are separating intramolecular bonds that keep the molecule together. These bonds are strong covalent bonds which take a lot of energy to break, so a lot of heat energy is required before the bonds will break to boil or melt; meaning they have high melting and boiling points.

1.42 explain why substances with simple molecular structures have low melting and boiling points in terms of the relatively weak forces between the molecules

A substance with a simple molecular structure is one that contains only a few atoms in a molecule.
The intermolecular forces (between the molecules) are weak, so it doesn't take much energy- or heat- to break them- this means they will melt and boil under low heats, as even small amounts of heat energy are enough to break the bonds.

1.41 understand that substances with simple molecular structures are gases or liquids, or solids with low melting points

A simple molecule (one with only a few atoms) will have a low melting point.