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Chemistry > Chemical Changes > Flashcards

Chemical Changes Flashcards

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1
Q

What is a base?

A

bases are compounds that can neutralise an acid

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2
Q

What is an alkali?

A

alkali’s are bases that are soluble in water

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3
Q

What are the acid general equations?

A

acid + base –> salt + water
acid + metal –> salt + hydrogen
acid + metal oxide –> salt + water
acid + metal hydroxide –> salt + water
acid + metal carbonate –> salt + carbon dioxide + water
acid + ammonia solution –> ammonium salt + water

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4
Q

What does acid + base -> ?

A

salt + water

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5
Q

What does acid + metal -> ?

A

salt + hydrogen

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6
Q

What does acid + metal oxide ->

A

salt + water

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7
Q

What is a neutralisation reaction?

A

an acid and alkali reaction

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8
Q

How to remember the neutralisation reactions?

A
  • acid = proton donor (hydrogen ion)
  • remember all reactions create a salt
  • remember law of conservation of atoms (if carbon is in reactants, it must be in products)
  • if hydrogen and/or oxygen are reactants, water will be a product
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9
Q

What is the reactivity series?

A

Please Stay Late Cause My Awesome Cat Zinc Is Hyper Chaotic Silly Girl

  • Potassium
  • Sodium
  • Lithium
  • Calcium
  • Magnesium
  • Aluminium
  • Carbon -!
  • Zinc
  • Iron
  • Hydrogen
  • Copper
  • Silver
  • Gold
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10
Q

What are weak acids?

A

Weak acids = acids that partially ionise/dissociate, releasing H^+ ions

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10
Q

What is a salt?

A

When an hydrogen leaves an acid, and bonds with metals.

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10
Q

What are need to know ions?

A

NO3^2- : nitrate ions
SO4^2- : sulfate ion
NH4^+ : ammonium ion
CO3^2- : carbonate ion

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10
Q

Are hydroxide ions alkali or acidic?

A

OH- = alkali

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10
Q

What are strong acids?

A

acids that completely ionise/dissociate, releasing H^+ ions

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11
Q

Examples of strong acids?

A

HCl
H2SO4
HNO3

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11
Q

Examples of weak acids?

A

ethanoic acid = vinegar
citric acid
carbanoic (rain water, fizzy drinks)

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12
Q

What does acid + metal hydroxide -> ?

A

salt + water

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13
Q

What does acid + metal carbonate -> ?

A

salt + carbon dioxide + water

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14
Q

What does acid + ammonia solution -> ?

A

ammonium salt + water

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15
Q

How do you measure the pH of a solution?

A

Indicator- dye that changes colour depending on pH

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16
Q

What is an example of a wide range indicator?

A

universal indicator
- contains a mixture of dyes, gradually change colour for a wide range of pH
- useful estimating pH of a solution

pH probe
- attached to a pH meter, electronic measurement
-numerical result, more accurate

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17
Q

What ions do alkali’s form in water?

A

OH^-

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18
Q

What ions do acid produce in water?

A

H^+ (hydrogen ions)

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19
Q

Is the ionisation of a weak acid a reversible reaction?

A

Yes, it sets up an equilibrium between the undissociated and dissociated acid. (less H^+ ions are released, equilibrium lies to the left)

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20
Q

How does concentration of H^+ ions affect rate of reaction?

A

High concentration: rate of reaction is faster, strong acids are more reactive than weak acids of same concentration.

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21
Q

What is pH?

A

a measure of concentration of H^+ ions

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22
Q

If the pH scale decreases by 1, how does the concentration of H+ ions change?

A

increases by a factor of 10
(pH 4 = 10x concentration of H+ than pH 5)

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23
Q

If the pH scale decreases by 2, how does the concentration of H+ ions change?

A

increases by a factor of 100

24
Q

What is the formula for the factor of H+ ion concentration when pH changes?

A

Factor H+ ion concentration changes by = 10 ^-x
x= difference in pH

25
Q

What does acid strength tell you?

A

What proportion of the acid molecules ionise in water

26
Q

What does the concentration of an acid tell you?

A

How much acid there is in a certain volume of water

27
Q

How is reactivity determined in metals?

A

By how easily they lose electrons, forming positive ions

28
Q

How is the speed of a reaction indicated by?

A

the rate at which hydrogen bubbles are given off

29
Q

What is the relationship between reactive metals and the rate of reaction?

A

The more reactive the metal, the faster the reaction
(Pottasium, Sodium, Lithium react explosively- more reactive)
(magnesium, zinc, iron react less violently- less reactive)
(copper- barely no reaction)

30
Q

How can you investigate the reactivity of metals?

A
  • measuring the temperature change of the reaction (with acid or water), over set period of time
  • if same mass + SA of metal, the more reactive the metal= greater the temperature change will be
31
Q

What does water + metal -> ?

A

Metal oxide + Hydrogen

more reactive metals will react, less reactive metals won’t react

32
Q

What is a reduction reaction?

A

A type of oxidation reaction
- a reaction that separates a metal from its oxide

33
Q

What is an oxidation reaction?

A
  • the loss of electrons
  • gain of oxygen
34
Q

What is a reduction reaction?

A
  • the gain of electrons
  • the loss of oxygen
35
Q

What type of reaction is the formation of a metal ore?

A

Oxidation

36
Q

What type of reaction is the extraction of metal?

A

Reduction

37
Q

How can metals be extracted from their ores (chemically)?

A

Reduction with carbon:
- ore reduced (looses oxygen)
- carbon oxidised, CO2 (gains oxygen)

38
Q

What determines if the metal can be extracted with carbon or not?

A

The position of the metal in the reactivity series

39
Q

How are metals more reactive than carbon extracted from their ores?

A

Electrolysis
(expensive)

40
Q

How are metals less reactive than carbon extracted from their ores?

A

Using reduction by carbon
(iron oxide in a blast furnace = iron)
- Carbon can only rake oxygen away from metals which are less reactive than itself

41
Q

How is gold mined?

A

Found in the earth as itself, so unreactive
- mined in elemental form

42
Q

What is a displacement reaction?

A

When a more reactive metal will displace a less reactive metal from its compound

43
Q

In displacement reactions, what always happens to the metal ion?

A

The metal ion always gains electrons + is reduced

44
Q

What is a spectator ion?

A

ions that don’t change in the reaction

45
Q

What is an ionic equation?

A

An equation that just focuses on the substances being oxidised and reduced

46
Q

What is Electrolysis?

A

A process that uses an electrical current to cause a reaction

47
Q

What is the process of Electrolysis?

A

-An electric current is passed through an electrolyte, ions move to electrodes + react (compound is dissolved)
- Positive ions move towards the cathode + gains electrons (reduced)
-Negative ions move towards the anode + lose electrons (oxidised)
-Creates flow of charge in electrolyte as ions travel to electrode
-As ions gain or lose electrons, they form uncharged elements and are discharged from the electrolyte

48
Q

What is an Electrolyte?

A

A molten or dissolved ionic compound
- can conduct electricity
- electrode is submerged in electrolyte

49
Q

What is an Electrode?

A

a solid that conducts electricity, is submerged in an electrolyte

50
Q

What is a cathode?

A

negative electrode

51
Q

What is an anode?

A

positive electrode

52
Q

Why can’t an ionic solid be electrolysed?

A

Ions are in fixed position, cannot move

53
Q

How are molten ionic liquids broken up into their elements using electrolysis?

A

-Positive metal ions are reduced to the element at the cathode

-Negative non-metal ions are oxidised to the element at the anode

53
Q

Why can molten ionic compounds be electrolysed?

A

Ions can move freely, conduct electricity

54
Q

How can metals be extracted from their ores using electrolysis?
(EG. Aluminium)

A

-Aluminium is extracted from Bauxite (ore, contains aluminium oxide) by electrolysis.
- Aluminium oxide-> High melting temp, mixed w Cryolite to lower melting point
- molten mixture contains free ions-> conducts electricity
- Positive Al^3+ ions -> negative electrode, become neutral Al atoms, sink to bottom of tank
- Negative O^2- ions attracted to positive electrode, lose 2 electrons, neutral O atoms combine, forming O2 molecules
-

55
Q

What is Cryolite?

A
  • aluminium based compound, lower melting point than aluminium oxide
56
Q

What is the process of Electrolysis of Aqueous solutions?

A
  • In aqueous solutions, H+ and OH- ions are also present from the water (as well as the ionic compound)
  • Cathode: hydrogen gas may be produced if H+ and metal ions are present and the metal ions form a elemental metal more reactive than hydrogen (ie sodium ions). If they produce a elemental metal less reactive (copper ions), solid layer of pure metal produced
  • Anode: if OH- and Halide ions (Cl-, Br, I-) are present, molecules of the halide are produced. If no halide present, OH- ions discharged, oxygen formed
57
Q

What is the neutralisation reaction between Hydrogen and Hydroxide ions?

A

H+ + OH- -> H2O

58
Q

How do you test for Chlorine?

A

Damp piece of litmus paper, bleaches it, turning it white

59
Q

How do you test for Hydrogen?

A

Take a test tube with the gas inside, take a lit splint place inside, if ‘squeaky pop’ sound is made, gas is present

60
Q

How do you test for Oxygen?

A

Take a test tube with the gas present, take a splint and light it, blow it out ( a glowing split), place glowing splint inside if gas is present the splint will relight

61
Q

What is acid + metal hydroxide –> ?

A

salt + water

62
Q

What is acid + metal carbonate –> ?

A

salt + carbon dioxide + water

63
Q

What is acid + ammonia solution –> ?

A

ammonium salt + water

Chemistry (13 decks)

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