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chemical changes Flashcards

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1
Q

what is reduction?

A

loss of oxygen, gaining of electrons

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2
Q

what is oxidation?

A

gain of oxygen, loss of electrons

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3
Q

what is a native metal?

A

metal found uncombined in the earth eg gold, copper, platinum

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4
Q

what is an ore?

A

a rock that contains enough metal to make it profitable to extract

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5
Q

how are less reactive metals extracted?

A

they are reacted with carbon- redox reaction

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6
Q

how are reactive metals extracted?

A

electrolysis

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7
Q

metal + acid -> ..?

A

salt + hydrogen

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8
Q

acid + base -> ..?

A

salt + water

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9
Q

acid + carbonate -> …?

A

salt + water + co2

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10
Q

what ions are in acids?

A

H+ ions

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11
Q

what ions are in alkalis?

A

OH- ions

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12
Q

what is neutral pH?

A

7

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13
Q

what is acid pH?

A

less than 7

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14
Q

what is alkaline pH?

A

more than 7

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15
Q

what happens at the cathode?

A

positive electrode- reduction occurs

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16
Q

what happens at the anode?

A

negative electrode- oxidation occurs

17
Q

why can ionic substances only conduct electricity when molten/dissolved?

A

the ions are not in fixed positions- they are free to move and carry charge

18
Q

what forms at the cathode in aqueous electrolysis?

A

if the metal is MORE reactive than hydrogen, then hydrogen will be produced at the cathode. if the metal is less reactive, then it will form.

19
Q

what forms at the anode in aqueous electrolysis?

A

if halides are present then halogens form. if not, oxygen is formed from hydroxide ions in water.

20
Q

what is the test for hydrogen?

A

lit splint produces a squeaky pop

21
Q

what is the test for chlorine?

A

bleaches damp litmus paper- turns blue to red to white

22
Q

what is the test for oxygen?

A

relights a glowing splint

23
Q

what is the test for carbon dioxide?

A

turns limewater cloudy

24
Q

why is electrolysis so expensive as an extraction method?

A

requires a lot of energy- to melt the compound and produce electrical current

25
Q

what is cryolite and what is its purpose?

A

a substance added to aluminium oxide- lowers the melting point so it reduces the energy required

26
Q

what are the electrodes made of in electrolysis of aluminium?

A

graphite

27
Q

why does the anode need regular replacement in aluminium extraction?

A

oxygen is produced at the anode which reacts with graphite in the anode to form carbon dioxide which wears down the anode

chemistry (10 decks)

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