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Chemistry > Chemical Changes > Flashcards

Chemical Changes Flashcards

1
Q

What is a wide range indicator

A
  • an indicator that contains a mixture of dyes that means they gradually change colour over a broad range of ph
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2
Q

How to measure ph electronically

A
  • a pH probe is attached to a pH meter
  • the probe is placed n the solution you are measuring and the pH is given on a digital display as a numerical value
  • its more accurate than a indicator
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3
Q

What is an acid

A
  • a substance that forms aqueous solutions with a pH less than 7
  • it forms H+ ions in water
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4
Q

What is a base

A

A substance with a pH greater than 7

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5
Q

What is an alkali

A
  • abase that dissolves in water to form a solution with a pH greater than 7
  • alkalis form OH- ions in water
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6
Q

Word equation for neutralisation

A

Acid + base — salt + water

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7
Q

Symbol equation of neutralisation

A

H+ + OH- — H2O

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8
Q

What happens to strong acids in water

A
  • they ionise completely
  • all acid particles dissociate to release H+ ions
  • eg. HCL — H+ + CL-
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9
Q

Examples of strong acids

A
  • sulfuric
  • hydrochloric
  • nitric
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10
Q

Examples of weak acids

A
  • Ethanoic
  • citric
  • carbonic
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11
Q

What happens to weak acids in solutions

A
  • they don’t dully ionise
  • only a small proportion of acid particles dissociate to release H+ ions
  • its a reversible reaction
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12
Q

Is a strong acid more reactive than a weak acid

A
  • if the concentration of H+ ions is higher, the rate of reaction will be higher
  • strong acids will be more reactive than weak ones if at the same concentration
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13
Q

What is pH

A
  • the pH of an acid or alkali is the measure of the concentration of H+ ions in the solution
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14
Q

Rule of concentration of H+ ions in an acid

A

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

X is the difference in pH
An acid that has the pH 4 has 10 times the concentration of H+ ions of an acid with pH 5
- so pH of a strong acid is always less than the pH of a weaker acid if they have the same concentration

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15
Q

What is acid strength

A

Tells us what proportion of the acid molecules ionise in water

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16
Q

What does acid + metal oxide produce

A

Salt + water

17
Q

What does acid + metal hydroxide produce

A

Salt + water

18
Q

What does acid + metal carbonate produce

A

Salt + water + carbon dioxide

19
Q

How to make soluble salt using an insoluble base

A
  1. You need to pick the right acid ad insoluble base, such as an insoluble metal oxide, hydroxide or carbonate
  2. Gently warm the dilute acid using a Bunsen burner, then turn off Bunsen burner
  3. Add the insoluble base to the acid a bit at a time until no more reacts. The acid will be neutralised wen seven after stirring, the excess solid will just sink to the bottom of the flask
  4. The filter out the excess solid to get the salt solution
  5. To get pure solid crystals of the salt, gently heat the solution using a water bath or an electric heater to evaporate some of the water and then stop heating it and leave solution to cool. Crystals should start to form, which can be filtered out of the solution and then dried
20
Q

Reactivity series order

A

Potassium
Sodium
Lithium
Calcium
Magnesium
CARBON
Zinc
Iron
HYDROGEN
Copper

21
Q

What does the reactivity series tell us

A
  • reactivity is determined by how easily they lose electrons and form positive ions
  • when metals react with water or acid, they lose electrons and form positive ions
  • so the higher a metal is in the reactivity series, the mor easily it reacts with water or acid
22
Q

How metals react with acids tells you about their reactivity

A
  • some metals react with acids to produce a salt an hydrogen gas
  • the speed of the reaction is indicated by the rate a which the bubbles of hydrogen are given off
  • the more reactive the metal, the faster the reaction will go
23
Q

Word equation for when a metal reacts with water

A

Metal + water — metal hydroxide + hydrogen

24
Q

What metals will react with water

A

Potassium, sodium, lithium, calcium

25
Q

What metals wont react with water

A

Less reactive one like since, iron and copper

26
Q

Formation of metal ore

A
  • oxidation
  • magnesium is oxidised to make magnesium oxide
27
Q

What is oxidation

A

Gain of oxygen

28
Q

Extraction of metal

A
  • reduction
  • copper oxide is reduced to copper
29
Q

What is reduction

A

Loss of oxygen

30
Q

What is an ore

A

A type of rock that contains metal compounds

31
Q

How are metals above carbon in the reactivity series extracted from their metals ores

A
  • electrolysis which is expensive
32
Q

How are meals below carbon in the reactivity series extracted

A
  • reduction using carbon
  • this because carbon can only take the oxygen away from the metals which are less reactive than carbon itself
33
Q

Action of reduction using carbon

A
  • the ore is reduced as oxygen is removed from it an carbon gain oxygen so is oxidised
34
Q

OIL RIG

A

Oxidation Is Loss of electrons
Reduction Is Gain of electrons

35
Q

What is REDOX reaction

A

When reduction and oxidation happen at the same time
- all reactions of metals and acids are redox reactions

36
Q

Example of redox reaction (iron)

A
  • iron atoms are oxidised to Fe2+ ions when they react with dilute acid
  • the iron atoms lose electros. They’re oxidised by the hydrogen atoms
  • the hydrogen ions gain electrons. They’re reduced by the iron atoms
37
Q

What is a displacement reaction

A

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

38
Q

What happens to metal ions vs metal atoms in displacement

A
  • metal ion gains electrons and is reduced
  • metal atoms are oxidised and lose electrons
39
Q

Ionic equation vs whole displacement equation

A

Ionic equation only shows particles that react and the products:

Mg + Zn2+ — Mg2+ + Zn

Full equation:

Mg + ZnCl2 — MgCl2 + Zn

Or

Mg + Zn2+ + 2Cl- — Mg2+ + 2Cl- + Zn

Chemistry (11 decks)

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