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Chemistry > C3 Chemical changes > Flashcards

C3 Chemical changes Flashcards

1
Q

What ions does an acid form in solutions?

A

H+ ions

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2
Q

What ions does a base have?

A

OH- ions

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3
Q

What is a base?

A

any substance + acid –> salt + water

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4
Q

What is an alkali?

A
  • a soluble base
  • that dissolves in water
  • form OH- ions
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5
Q

What colour changes occur on red litmus paper?

A

acidic solution - red
neutral solution - red
alkaline solution - blue

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6
Q

What colour changes occur on blue litmus paper?

A

acidic solution - red
neutral solution - blue
alkaline solution - blue

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7
Q

What colour changes occur on litmus paper?

A

acidic solution - red
neutral solution - purple
alkaline solution - blue

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8
Q

What colour changes occur in methyl orange?

A

acidic solution - red
neutral solution - yellow
alkaline solution - yellow

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9
Q

What colour changes occur in phenolphthalein?

A

acidic solution - colourless
neutral solution - colourless
alkaline solution - pink

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10
Q

What is a neutral pH?

A

7

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11
Q

What is an acidic pH?

A

1-6

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12
Q

What is an alkaline pH?

A

8-11

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13
Q

How does the concentration of H+ ions affect pH?

A

high conc means lower pH

-more acidic

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14
Q

How does concentration of OH- ions affect pH?

A

high conc means higher pH

-more alkaline

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15
Q

How does H+ ion concentration in a solution affect pH?

A

As H+ ion conc increases by a factor of 10 pH decreases by 1

eg pH 5 x10H+ —> pH 4

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16
Q

If the pH decreases what has happened to the H+ ion concentration?

A

increased by a factor of 10

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17
Q

How is concentration different to acid strength?

A

concentration
-how much acid that is dissolved in 1 dm^3 of water

acid strength
-how much of the acid dissociates to form H+ ions

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18
Q

What is a strong acid?

A

strong acids completely ionise in water

-> dissociate to release H+ ions

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19
Q

What is a weak acid?

A

weak acids partially ionise in water
-> some molecules dissociate

ionisation of a weak acid is reversible

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20
Q

What makes an acid dilute?

A

if there is not a lot of acid in the solution

21
Q

What makes an acid concetrated?

A

if there is a lot of it in the solution

22
Q

What is the reaction between a base and acid?

A
  • neutralisation
  • salt and water formed only
  • water has neutral pH of 7
23
Q

How do you test for hydrogen?

A
  • lighted splint

- squeaky pop

24
Q

How do you test for carbon dioxide?

A
  • bubble gas through limewater

- turns cloudy white

25
Q

What products form from reacting a metal and acid?

A

metal + acid —> metal salt + hydrogen

26
Q

What products form from reacting a metal oxide and acid?

A

metal oxide + acid -> metal salt + water

27
Q

What products form from reacting a metal hydroxide and acid?

A

metal hydroxide + acid -> metal salt + water

28
Q

What products form from reacting a metal carbonate and acid?

A

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

29
Q

On an ionic level, why is an acid and alkali reaction neutralising?

A

acid + alkali -> water

H+ + OH- —> H2O

30
Q

What are electrolytes?

A

ionic compouns in a solution or liquid (molten) state

31
Q

What is electrolysis

A

breaking down of an ionic subtance using electrical energy

32
Q

Which electrode has a positive charge?

A

anode

33
Q

Which electrode has a negative charge?

A

cathode

34
Q

Where do positively charged cations migrate to during electrolysis?

A

negatively charged cathode

35
Q

Where do negatively charged anions migrate to during electrolysis?

A

positively charged anode

36
Q

What occurs at the anode?

A

oxidation

-loss of electrons

37
Q

What occurs at the cathode?

A

reduction

-gain of electrons

38
Q

What forms during the electrolysis of copper chloride solution?

A

anode

  • oxidation
  • loss of electrons
  • chlorine gas

cathode

  • reduction
  • gain in electrons
  • copper solid covers electrode
39
Q

What forms during the electrolysis of sodium chloride solution?

A

anode

  • oxidation
  • loss of electrons
  • chlorine gas forms

cathode

  • reduction
  • gain in electrons
  • hydrogen gas forms
40
Q

What forms during the electrolysis of sodium sulfate solution?

A

anode

  • oxidation
  • loss of electrons
  • oxygen forms

cathode

  • reduction
  • gain in electrons
  • hydrogen forms
41
Q

What forms during the electrolysis of water acidified with sulfuric acid? (H2O + H2SO4)

A

anode

  • oxidation -> hydroxide
  • loss of electrons
  • oxygen forms

cathode

  • reduction
  • gain of electrons
  • hydrogen forms
42
Q

What forms during the electrolysis of molten lead bromide?

A

anode

  • oxidisation
  • electron lost
  • bromine gas
  • seen as bubbles

cathode

  • reduction
  • electrons gained
  • molten lead forms at cathode
  • silver in colour
43
Q

When is the metal produced at the cathode and when is hydrogen produced instead?

A

metal produced
- if metal is less reactive than hydrogen
eg Cu, Ag, Au

hydrogen produced
- if metal is more reactive than hydrogen

44
Q

What are the half equations for the electrolysis of molten lead bromide?

A

anode
2Br- —> Br2 + 2e-

cathode
Pb2+ + 2e- —> Pb

45
Q

What are the half equations for the electrolysis of copper chloride?

A

anode
2Cl- —> Cl2 + 2e-

cathode
Cu2+ + 2e- —> Cu

46
Q

What are the half equations for the electrolysis of sodium chloride?

A

anode
2Cl- —> Cl2 + 2e-

cathode
2H+ + 2e- —> H2

47
Q

What are the half equations for the electrolysis of sodium sulfate?

A

anode
4OH- —> O2 + 2H2O + 4e-

cathode
2H+ + 2e- —> H2

48
Q

What are the half equations for the electrolysis of water acidified with sulfuric acid?

A

anode
4OH+ —> O2 + 2H2O + 4e-

cathode
2H+ + 2e- —> H2

Chemistry (10 decks)

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