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chemistry > Topic 4- chemical changes > Flashcards

Topic 4- chemical changes Flashcards

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1
Q

How do you use a pH probe?

A
  • pH probe attached to pH meter
    -probe placed in the solution
    -numerical value given- more accurate
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2
Q

What do acid form when dissolved in water?

A

Hydrogen ions (H+) - subscript

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3
Q

What do alkalis form when dissolved in water?

A

OH-
hydroxide ions

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4
Q

What is a neutralisation reaction?

A

acid + alkali -> salt + water

H+ + OH- -> H2O

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5
Q

What does a titration do?

A

Allows you to find out how much acid is needed to neutralise a certain quantity of alkali (and vice versa)

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6
Q

Method for titration?

A
  1. Use a pipette with a pipette filler to measure a volume of alkali (eg sodium hydroxide)
  2. Add 5 drops of indicator such as methyl orange to the alkali in a conical flask
  3. Fill a burette with the acid
  4. Add acid to the alkali until the solution until it is neutral
  5. Once we start to see a colour change, add acid drop by drop until the colour of the indicator changes. Swirl to mix
  • Methyl orange is yellow in alkalis and red in acids
    6. Read the volume of acid from the burette at the bottom of the meniscus. Use this value and the initial amount of acid in the burette to calculate the volume of acid used to neutralise alkali
    7. Repeat the process and calculate the mean volume of acid needed to neutralise the alkali, ignoring anomalous results to reduce random error and see if your experiment is repeatable
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7
Q

When acids are added to an aqueous solution

A

They ionise to produce H+ ions.

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8
Q

Examples of strong acids?

A

Sulfuric acid - H2SO4
Hydrochloric acid- HCl
Nitric acid- HNO3

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9
Q

What do strong acid do?

A

Strong acid ionise completely in water and the acid particles dissociate to release H+ ions

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10
Q

Examples of weak acid?

A

Carboxylic acids
Citric acid
Carbonic acids

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11
Q

What is a weak acid?

A

Weak acid partially ionise in water, only some of the acid molecules ionise and release H+ ions.

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12
Q

What type of a reaction is ionisation of a weak acid?

A

It is a reversible reaction which means is a equilibrium between the undissociated and dissociated acid molecules.

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13
Q

If the concentration of H plus ions in higher, the rate of reaction will be?

A

Faster.

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14
Q

Since strong acid dissociate more than weak acids..

A

A strong acid will be more reactive than a weak acid of the same concentration.

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15
Q

What is pH?

A

Measure of concentration of H+ ions in a solution.

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16
Q

If the pH is lower, what happens to the H+ ions and acidity?

A

The higher concentration of H+ ions and so the more acidic the solution is.

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17
Q

Will the pH of a strong acid be lower or higher than a weak acid?

A

Lower because strong acid dissociate more than weak acid resulting in a larger concentration of H+ ions.

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18
Q

How do you calculate the change in H+ concentration with the equation?

A

Factor H+ ion concentration changes by 10^-x

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19
Q

How do to questions with the factor H+ concentration changes by?

A
  1. Find the difference in pH after that addition of acid/alkali
    eg pH 7 to 4 = -3
  2. Substitute
    10-(-3)
  3. Calculate
    10x10x10= 1000
    H+ ion concentration in solution is 1000 times higher
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20
Q

What is the concentration of an acid?

A

Concentration measures the total number of dissolved acid molecules there are in a certain volume of water.

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21
Q

If the acid concentration increases, the pH will?

A

Decrease

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22
Q

What is a base?

A

Substances that react with acids in neutralisation reactions i.e. metal oxide or hydroxide

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23
Q

Soluable metal hydroxides are alkalis or acids?

A

Alkalis as they dissolve in water to form OH- ions

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24
Q

Equation for reaction of metal oxides/hydroxides with acids?

A

acid + metal oxide/hydroxide-> salt + water

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25
hydrochloric acid + copper oxide ?
copper chloride and water 2nd part of acid and first part of oxide/hydroxide chlorIDE sulfATE nitrATE
26
What is a metal carbonate?
Also a base
27
metal carbonate + acid ->
metal carbonate + acid -> metal salt + carbon dioxide + water
28
How can you make soluable salts?
-Reacting an acid with a metal or insoluable base eg metal oxide, hydroxide , carbonate
29
Method to make soluable salts from acid and insoluable bases
1. Put dilute acid and heat 2. Add insoluble reactant. It will form a soluble product as it reacts 3. Keep adding insoluble reactant until in excess. There will be some left over reactant that will not react - acid is neutralised 4. Filter out excess insoluable reactant to get salt solution - filter funnel and filter paper 5. Crystallisation of salt solution - Heat solution using water bath to make more concentrated - Leave to cool and crystals foem
30
Where is the reactivity of a metal derived from?
How easily it forms positive ions.
31
Reactivity series?
Potassium Sodium Lithium Calcium Magnesium **Carbon** Zinc Iron **Hydrogen** Copper Hydrogen and carbon are non metals - used to compare
32
acid + metal?
acid + metal -> salt + hydrogen
33
How can we measure the reactivity of metals with acids?
-Montoring rate of hydrogen production.
34
Which metals are reactive with acids?
Potassium, sodium, lithium and calcium react explosively Magnesium, zinc and iron react less violently Copper does not react with cold dilute acids
35
How can you detect the production of hydrogen
Hydrogen test Put a lit splint into the test tube of the metal and acid Squeaky pop if there is hydrogen Louder when more reactive
36
What salt is formed when you react metals with acids? eg hydrochloric acid and magnesium?
Hydrochloric acid + magnesium = magnesium chloride + hydrogen second part of acid and first part of metal
37
Metal + water? Calcium?
metal + water -> metal hydroxide + hydrogen calcium + water -> calcium hydroxide + hydrogen
38
Which metals react with water?
Potassium, sodium lithium and calcium.
39
What is a displacement reaction?
Displacement reactions involve one metal replacing another out of a compound
40
A ___ reactive metal will displace a _____ reactive metal from its compound
More, less
41
What happens when you put a more reactive metal in the solution of a dissolved metal compound containing a less reactive metal ion?
The reactive metal will replace the less reactive metal in the compound
42
What happens when you place iron in a solution of copper sulfate?
The more reactive iron will replace the copper from the solution. You will end up with iron sulfate in the solution and copper as a precipitate iron + copper (II) sulfate -> iron(II) sulfate + copper
43
Where do we get metals from?
A few unreactive metals are found in the Earth as themselves. The rest are extracted from metal ores, which are normally metal oxides
44
Oxidation?
Oxidation is the gain of oxygen (and loss of electrons) by the element or compound
45
Reduction?
Loss of oxygen (and gain of electrons from a compound)
46
How can metals lower than carbon in the reactivity series be extracted?
Through a reduction reaction
47
How are metals above carbon in the reactivity of metals extracted
By electrolysis
48
How are metals extracted by reduction with carbon? Why?
In the reaction, the ore is reduced as oxygen is removed from it and the carbon gains oxygen so it is oxidised. The carbon can only take the oxygen away from metals that are less reactive than carbon itself.
49
When do redox reactions occur?
Redox reactions occur when electrons are transferred between substances.
50
OIL RIG
Oxidation loss electrons Reduction is gain
51
What type of reaction is a displacement reaction?
A redox reaction
52
What happens in displacement reactions? - what gains and looses electrons?
The metal ion gains electrons and is reduced. The metal atom loses electrons and is oxidised
53
What type of a reaction is an acid and metal?
A redox reaction
54
What happens when acids react with metals? What type of a reaction are they and why?
They form salts and release hydrogen. They are redox reactions because the metal atoms looses electrons and the hydrogen ions gain electrons
55
What happens during electrolysis?
An electric current is passed through a molten or dissolved iconic compound which then decomposes
56
What is electrolytes?
The liquid used to conduct the electricity. They contain free ions which move throughout the substance and carry an electric charge which conduct the electricity
57
PANIC
Positive anode Negative is cathode
58
REDCAT
REDuction CAThode
59
ANOX
Anode oxidation
60
OILRIG
Oxidation is loss of electrons Reduction is gain of electrons
61
LIPGIN
Loss is positive again is negative (electrons)
62
Electrolysis diagram
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chemistry (5 decks)

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