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chemistry > topic 4 - chemical changes > Flashcards

topic 4 - chemical changes Flashcards

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1
Q

how to measure the pH

A
  • indicator - changes colour
  • pH probe attatched to a pH meter
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2
Q

acids

A
  • pH less than 7
  • form H+ ions in water
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3
Q

base

A
  • pH greater than 7
  • alkali is a base that dissolves in water
  • alkalis form OH- ions in water
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4
Q

neutralisation reaction equation

A

acid + base –> salt and water

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5
Q

apparatus to titration

A
  • pipette - volume of solution
  • burette - drop by drop
  • concile flask
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6
Q

what colour will titration go

A
  • phenolphthalein is pink in alkali
  • colourless in acid
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7
Q

how to increase accuracy of titration

A
  • do a rough titration first so that when you know roughly where it will change colour then you can do much smaller and closer intervals
  • remove anomalous results
  • repeat multiple times
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8
Q

strong acids

A
  • ionise completely in water
  • all particles dissociate to release H+ ions
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9
Q

weak acids

A
  • don’t fully ionise
  • small amounts dissociate and release H+ ions
  • equilibrium lies to the left
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10
Q

the science behind what the pH is a measure of

A

the concentration of H+ ions in a solution

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11
Q

what is the strength of an acid

A

what proportion of the acid molecules ionise in water

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12
Q

what is the concentration of an acid

A

how much acid there is in a certain volume of water
- the larger amount of acid - the more concentrated

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13
Q

equation for neutralisation reaction of metal oxides and metal hydroxides

A

acid + metal oxide —> salt + water
acid + metal hydroxide —> salt + water

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14
Q

equation for the reaction of metal carbonates

A

acid + metal carbonate —> salt + water + carbon dioxide

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15
Q

reactivity series

A

Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper

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16
Q

how are metals ordered in the reactivity series

A

how easily they can loose electrons to form positive ions

17
Q

which metals react with water and equation

A

potassium, sodium, lithium, calcium
metal + water —> metal hydroxide + hydrogen

18
Q

what happens when metals react with acids

A

create a salt and produce hydrogen gas

19
Q

whats oxidation and reduction

A

oxidation: gain of oxygen - loss of electrons
reduction: loss of oxygen - gain of electrons

20
Q

which metals can be extracted from carbon and which from electrolysis

A
  • higher than carbon = electrolysis - ££££££
  • below carbon = by reduction using carbon
21
Q

whats a redox reaction

A

oxidation and reduction happening at the same time

22
Q

definition of a displacement reaction

A

a more reactive metal displacing a less reactive metal from its compound

23
Q

basics of electrolysis

A
  • electrcial current passed through electrolyte and their ions move toards the electrodws where they react and the compound decomposes
24
Q

anode and cathode in ELECTROLYSIS

A

POSITIVE ANODE (loss electrons and get oxidised)
NEGATIVE CATHODE (gain electrons and be reduced)

25
Q

why CANT an ionic solid be used in electrolysis

A
  • bc the ions are fixed and cant move
  • solution - molten ionic compound bc ions can move freely and conducts electricity
26
Q

how is aluminion extracted during electrolysis - molten

A

aluminion has to be extracted from its ore bauxite by electrolysis
1. aluminion oxide mixed with cryolite to lower melting point - molten mixture - conduct electricity
2. positive Al3+ go to negative cathode and gain 3 electrons and sink to bottom of tank
3. negative O2- ions go to positive anode and lose 2 electrons which then combine to form O2 molecules

27
Q

word and chemical equation for electrolysis of aluminion

A

aluminion oxide —> aluminion + oxygen

28
Q

electrolysis of aqueous solutions - what happens at the cathode and anode

A
  • CATHODE - if H+ ions and metal ions are present then HYDROGEN GAS will form if more reactive than hydrogen. if less reactive than hydrogen a solid layer of pure metal will be produced instead
  • ANODE - if OH- and halide ions are present then chlorine/bromine/iodine will be formed. if no halide ions are present then the OH- ions are discharged and oxygen will form- bubbles
29
Q

what ions are there in water

A

H+ and OH-

30
Q

half equation for electrolysis at cathode - aluminion

A

Al3+ + 3e- —> Al

31
Q

half equation for electrolysis at anode - oxygen

A

2O2- —> O2 + 4e-

chemistry (17 decks)

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