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CHEM 2.0 > Chemical Changes > Flashcards

Chemical Changes Flashcards

1
Q

metal + oxygen = ?

A

metal oxide

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2
Q

metal + water = ?

A

metal hydroxide + hydrogen

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3
Q

metal + acid = ?

A

salt + hydrogen

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4
Q

metal oxide + acid = ?

A

salt + water

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5
Q

metal hydroxide + acid = ?

A

salt + water

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6
Q

what is oxidation?

A

the loss of electrons

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7
Q

what is reduction?

A

the gain of electrons

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8
Q

list the reactivity series.

A

potassium
sodium
lithium
calcium
magnesium
aluminium
carbon
zinc
iron
sulfur
lead
hydrogen
copper
silver
gold
platinum

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9
Q

metal carbonate + acid = ?

A

salt + water + carbon dioxide

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10
Q

what happens in a displacement reaction?

A

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

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11
Q

which metals react with cold water?

A
  • K, Na, Li, and Ca fizz in cold water
  • Mg will fizz slightly over a longer period of time
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12
Q

which metals react with dilute acids?

A

most more reactive than hydrogen (potassium, sodium, lithium, calcium, magnesium, zinc, iron)

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13
Q

what do metals form when they react?

A

positive ions

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14
Q

what is a spectator ion?

A

an ion that doesn’t change within a reaction

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15
Q

what is the reduction half equation?

A

x^+ + e^- = x

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16
Q

what are the 2 oxidation half equations?

A
  • x^- = x + e^-
  • x = x^+ + e^-
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17
Q

what are the diatomic elements?

A

hydrogen, nitrogen, fluorine, oxygen, iodine, chlorine, bromine (have no fear of ice cold beverages)

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18
Q

what is an ore?

A

a rock containing a metal compound which metal can be extracted from for a profit

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19
Q

what are 3 types of metal extraction?

A
  • electrolysis
  • displacement using carbon (any less reactive than carbon)
  • thermal decomposition (mercury, silver)
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20
Q

why does gold not need to be extracted from ores?

A

it is unreactive so is found pure in the earth

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21
Q

what is the formula for hydrochloric acid?

A

HCl

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22
Q

what salt does hydrochloric acid form?

A

chloride

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23
Q

what is the formula for nitric acid?

A

HNO3

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24
Q

what salt does nitric acid form?

A

nitrate

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25
Q

what is the formula for sulphuric acid?

26
Q

what salt does sulphuric acid form?

27
Q

what is an acid?

A

a substance which contains H+ ions which are released when it is dissolved in water

28
Q

what does a low pH mean?

A

high concentration of H+ ions

29
Q

what is a strong acid?

A

where all molecules ionise - dissociate into ions

30
Q

what is a weak acid?

A

where only small fraction of molecules ionise - dissociate into ions - reversible and never goes to completion

31
Q

what is a concentrated acid?

A

lots of acid dissolved - high number of moles per dm^3

32
Q

what is a dilute acid?

A

small amount of acid dissolved - low number of moles per dm^3

33
Q

give the ionic equation for a neutralisation reaction

A

H^+ + OH^- → H2O

34
Q

what is pH?

A

a measure of the H+ concentration in solution

35
Q

what happens as pH decreases by 1 unit?

A

concentration of H+ ions increase by a factor of 10

36
Q

what is an alkali?

A

a substance which releases OH- ions when added to water

37
Q

what is a base?

A

a compound which neutralises acids

38
Q

give 3 examples of bases

A

metal oxides, metal hydroxides, metal carbonates

39
Q

what is electrolysis?

A

splitting of a compound using flow of charge

40
Q

what is an electrolyte?

A

ionic compound that is molten or dissolved in water that conducts electricity and is decomposed by it

41
Q

what is an electrode?

A

unreactive material which can conduct electricity - usually graphite

42
Q

why is graphite used for electrodes?

A
  • it has a high MP
  • it is inert
  • it conducts electricity
43
Q

what is the charge of anode and cathode in electrolysis?

A

positive anode, negative is cathode

46
Q

what is the product at the anode in electrolysis?

A

halogen gas (if anion is group 7) or oxygen (if anion is not group 7)

47
Q

what is cryolite?

A

aluminium compound with a lower melting point than aluminium oxide

48
Q

why is cryolite used in electrolysis?

A

using molten cryolite as a solvent reduces some of the energy costs involved in extracting aluminium by allowing the ions in aluminium oxide to move freely at a lower temperature.

49
Q

what is the process at the anode in electrolysis?

50
Q

give the half equation at the anode in electrolysis

A

X^- = e^- + X

51
Q

what is the product at the cathode in electrolysis?

A

metal (if cation is less reactive than hydrogen) or hydrogen (if cation is more reactive than hydrogen)

52
Q

what is the process at the cathode in electrolysis?

53
Q

give the half equation at the cathode in electrolysis

A

X^+ + e^- = X

54
Q

what is an anion?

A

negative ion

55
Q

what is a cation?

A

positive ion

56
Q

what is uncertainty?

A

systematic error which affects everything the same

57
Q

what colour is phenolphthalein?

A
  • pink in alkali
  • colourless in acid
58
Q

what is titration used for?

A

to make a soluble salt from an acid and soluble base
it is the best method to make sure reactants are mixed in correct proportions

59
Q

what are the control variables in titrations?

A

concentration and volume of acid

60
Q

what are concordant results?

A

within 0.1 of each other

61
Q

a piece of magnesium is placed in a solution of copper(II) sulfate; describe what you would observe.

A

magnesium would displace copper so a brown solid appears over the magnesium and the blue solution becomes paler

62
Q

compare the electrolysis of molten magnesium chloride with the electrolysis of aqueous magnesium chloride.

A

in MOLTEN:
- high temperature required to melt MgCl2
- Mg2+ ions attracted to cathode - Mg2+(l) + 2e- ⇒Mg(s)
- Cl- ions attracted to anode - 2Cl- ⇒Cl2(g) +2e-

in AQUEOUS:
- carried out at RT
- mixture of ions present: Mg2+, H+, Cl-, OH-
- Mg2+ and H+ ions attracted to cathode; hydrogen is less reactive than Mg and is more easily reduced so 2H+(l) + 2e- ⇒ H2(g)
- Cl- and OH- ions attracted to anode; chlorine is a halogen so 2Cl-(l) ⇒ Cl2(g) + 2e-

CHEM 2.0 (14 decks)

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