Chemical changes Flashcards

Question

Which two processes can be used to extract metals from their oxides? When do you which?

Answer 1

Reduction: when metal is below carbon on reactivity series. Electrolysis: when metal is above carbon in reactivity series.

Answer 2

It's expensive.

Answer 3

The gain of oxygen.

Answer 4

The loss of oxygen.

Answer 5

Unreactive metals like gold.

Answer 6

The loss of electrons.

Answer 7

The gain of electrons.

Answer 8

.beaker .electrolyte (a molten or dissolved ionic compound) .electrodes (cathode and anode) .battery .wires

Answer 9

1) An electric current is passed through an electrolyte. The ions move towards the electrodes, where they react, and the compound decomposes. 2) The positive ions move towards the cathode and gain electrons (they are reduced) 3)The negative ions move to the anode and lose electrons (they are oxidised) 4)This creates a flow of charge through the electrolyte as ions travel to the electrodes 5)As ions gain or lose electrons, they form uncharged element and are discharged from the electrolyte.

Answer 10

The ions are in fixed position and can't move.

Answer 11

When molten or dissolved because the ions are free to move through the structure and conduct electricity.

Answer 12

It's a good conductor and it's cheap

Answer 13

1)Aluminium has a very high melting point so it's mixed to cryolite to lower it. 2) The molten mixture contains free electrons so it'll conduct electricity. 3)The AL+ ions are attracted to the cathode where they pick up 3 electrons to turn into neutral aluminium atoms then sink to the bottom 4) The O2- ions are attracted to the positive electrode where they lose two electrons. The neutral oxygen atoms will combine to form O2 MOLECULES.

Answer 14

The water separates in H+ ions and OH- ions. The H+ ions are attracted to the cathode. The OH- ions are attracted to the anode. OH- ions are discharges to form neutral hydrogen atoms and oxygen atoms (the oxygen atoms combine).

Answer 15

Oxygen is produced at anode. The anode is made of carbon so it reacts with oxygen to produce carbon dioxide.

Answer 16

H20 ->(reversible) H+ + OH-

Answer 17

If the element is more reactive than hydrogen, hydrogen will be produced. If the element is less reactive than hydrogen, a solid layer of the pure metal is produced instead.

Answer 18

If the element is a halide, the halogen will be formed. If no halide present, the OH- ions are discharged and oxygen will be formed.

Answer 19

TO find out how much acid is needed to neutralise a quantity of alkali or vice versa.

Answer 20

. Repeat tests and calculate a mean result . Use concordant results

Answer 21

1)Using a pipette and a pipette filler add a set volume of alkali to conical flask. 2)Add two to three drops of indicator 3)Use a funnel to fill a burette with some acid of known concentration. Record initial volume of acid- do below eye level to avoid getting acid in eye 4)Using burette, add acid to alkali bit at a time giving the conical flask a regular twirl 5)Slow near end and stop when indicator changes colour. 6)Record final volume and use initial volume to calculate volume needed of acid to neutralise.

Answer 22

Can add in small increments .More accurate than a measuring cylinder.

Answer 23

Methyl orange: acid- red alkali- yellow Phenolphthalein: acid- colourless alkali-pink Litmus: acid- red alkali- purple

Answer 24

1) Gently warm dilute solution using Bunsen burner. Then turn off Bunsen burner. 2)Add the insoluble base to the acid bit at a time until no more reacts (if stirred excess solid will just sink to bottom of flask) 3) Then filter out the excess solid to get the salt solution. 4) To get pure solid crystals, do crystallisation- heat gently using water bath to make it more concentrated then stop heating and leave solution to cool. Filter out solution then leave to dry.