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Chemistry > C4 - Chemical Changes > Flashcards

C4 - Chemical Changes Flashcards

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1
Q

What do metals react with oxygen to form?

A

Metal oxides

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2
Q

Oxidation is X of oxygen
Reduction is Y of oxygen

A

X = gain
Y = loss

OILRIG

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3
Q

What is oxidation and reduction in terms of electrons?

A

Oxidation = loss of electrons
Reduction = gain of electrons

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4
Q

What is the reactivity of a metal related to?

A

Its tendency to form positive ions

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5
Q

How does the way in which metals react inform you about their reactivity?

A

A more reactive metal will displace a less reactive one

More reactive metals will experience a greater temperature change

More reactive metals will react more quickly. The speed of reaction is indicated by the rate at which bubbles are given off

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6
Q

Unreactive metals such as gold are found in the earth as the metal itself. How are most metals found?

A

Most metals are found as compounds that require chemical reactions to extract the metal

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7
Q

How can metals less reactive than carbon be extracted?

A

From their oxides by reduction with carbon. Reduction involves the loss of oxygen

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8
Q

Order the reactivity series from most to least reactive

A

Potassium (K)
Sodium (Na)
Lithium (Li)
Calcium (Ca)
Magnesium (Mg)
Carbon (C)
Zinc (Zn)
Iron (Fe)
Hydrogen (H)
Copper (Cu)

Acronym: Please send lions, cats, monkeys (and) cute zebras into hot countries

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9
Q

What is electrolysis?

A

The passing of an electric current through ionic substances that are molten or in solution to split or break them down into elements

(Decomposition of a compound using direct current)

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10
Q

What are electrolytes?

A
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11
Q

Describe the process of molten electrolysis

A

Positively charged (metal) ions will move towards the cathode as opposites attract. Here, the ions will be discharged. A positive ion will gain electrons to become neutral to form the metallic element. This is an example of reduction

Negatively charged (non-metal) ions will move to the anode as opposites attract. Here, the non-metal ions will be discharged. They will loose elections by depositing it to become neutral to form the non-metallic element. Bubbles of the non-metallic gas will be observed. This is an example of oxidation

(The metal is produced at the cathode and the non-metal is produced at the anode)

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12
Q

How are metals placed in order of their reactivity?

A

Through their reactions with water and dilute acids

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13
Q

When is electrolysis used in the extraction of metals?

A

Electrolysis is used if the metal is too reactive to be extracted by reduction with carbon OR if the metal reacts with carbon

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14
Q

What is a disadvantage of using electrolysis to extract metals from molten compounds?

A

High yield (large amounts) of energy are used in the extraction process to melt the compounds and to produce the electrical current

Expensive

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15
Q

Why is a molten mixture of aluminium oxide and cryolite used as the electrolyte when electrolysing aluminium?

A

Aluminium is mixed with cryolite to reduce the melting point so that less energy is required to melt the aluminium. This makes it less expensive

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16
Q

What is the positive electrode (anode) used in the manufacturing of aluminium by electrolysis? Why does it continually need to be replaced?

A

Carbon is used as the positive electrode

The carbon electrode reacts with oxygen so carbon dioxide is produced

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17
Q

What do the ions discharged when an aqueous solution is electrolysed using inert electrodes depend on?

A

Relative reactivity of the elements involved

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18
Q

In the electrolysis of aqueous solutions, what is discharged at the negative electrode (cathode) and the positive electrode (anode)?

Why does this occur?

A

CATHODE: Hydrogen is produced if the metal is more reactive than hydrogen; if the metal is less reactive, it will be produced instead

ANODE: Oxygen is produced unless the solution contains halide ions; if the solution contains halide ions, the halogen gas is produced

This happens because in the aqueous solution water molecules break down producing hydrogen ions and hydroxide ions that are discharged.

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19
Q

What are the half equations for the reactions at the electrodes of molten aluminium oxide?

A

At the cathode: Al3+ + 3e- —> Al
At the anode: 2 02- —> O2 + 4e-

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20
Q

What ions does aluminium oxide contain?

A

Aluminium ion Al3+
Oxide ion O2-

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21
Q

Describe how to investigate what happens when aqueous solutions undergo electrolysis

A

Pour approx 50cm3 copper (II) chloride solution into a beaker

Place a plastic Petri dish over it with two holes. Insert a carbon graphite rod into each hole

Attach crocodile leads to the rods and connect them to the terminals of a power supply

Switch the power supply on at 4V. At the cathode, copper will be discharged as it is less reactive than hydrogen. At the anode, chlorine gas will form as it is a halide ion
This can be tested using a damp blue litmus paper that will bleach white in the presence of chlorine

Repeat the steps of the investigation using sodium chloride solution

At the anode, chlorine gas will be produced and this can be tested the same way. However, at the cathode, hydrogen gas will form as sodium is more reactive than hydrogen. Hydrogen can be tested using a lit splint. Hydrogen gas produces a squeaky pop

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22
Q

You have Quizlet flashcards for the other sciences. Get all the content done over summer. Read Jekyll and Hyde. Annotate power and conflict

A

X

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23
Q

The reactions of acids (hydrochloric acid and sulfuric acid) with metals (magnesium, zinc and iron) are examples of what type of reaction?

A

Redox

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24
Q

Define acid

A

Substance with a pH less than 7 which forms H+ ions

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25
Q

Define base

A

(Insoluble) Substance with a pH greater than 7

26
Q

Define alkali

A

Base that dissolves in water, forming OH- ions

27
Q

What does the particular salt produced in any reaction between an acid and an alkali/base depend on?

A
  • The acid used (nitric acid produces nitrates for example)
  • The positive ions in the base, alkali or carbonate
28
Q

Describe a method to make pure dry samples of named soluble salts (6)

-> Also, write down WHY you carry out each step

A
  • Add 40cm^3 of 1.0M (acid) into a 100cm^3 beaker. This is the limiting reactant
  • Add in excess the (insoluble oxide or carbonate)
  • Gently heat the acid on a tripod and gauze using a Bunsen burner until almost boiling
  • Stir with a glass rod until no more (insoluble oxide or carbonate) reacts. At this point, the solution is neutral
  • Filter to remove unreacted acid using a funnel and filter paper
  • Place the solution in an evaporating basin over a beaker acting as a water bath. Evaporate at least half the liquid
  • Pour the solution into a petri dish and allow it to crystallise for 48 hours. Finally, blot the crystals dry
29
Q

Examples of strong acids (HSN)

A

Hydrochloric acid
Nitric acid
Sulfuric acid

30
Q

Examples of weak acids (CCE)

A

Ethanoic acid (carboxylic acid)
Citric acid
Carbonic acid

31
Q

What do acids produce in aqueous solutions?

A

H+ ions

32
Q

What do aqueous solutions of alkalis contain?

A

Hydroxide ions (OH-)

33
Q

What is the pH scale range?

A

0-14

34
Q

What is the pH scale?

A

A measure of the acidity or alkalinity of a solution

35
Q

How can the acidity or alkalinity of a solution be measured?

A

Using a universal indicator or a pH probe

36
Q

AT3 This is an opportunity to investigate pH changes when a strong acid neutralises a strong acid

A
37
Q

What is a solution with pH 7 called?

A

Neutral

38
Q

What pH values do aqueous solutions of acids have?
Similarly, what pH values do aqueous solutions of alkalis have?

A

pH values of less than 7
pH values greater than 7

39
Q

In neutralisation reactions between an acid and an alkali, what is formed?

Write it also as a chemical equation

A

Hydrogen ions react with hydroxide ions to produce water

H+ (aq) + OH- (aq) —-> H20 (l)

40
Q

Describe the use of universal indicator or a wide range indicator to measure the approximate pH of a solution

A
41
Q

Describe how to carry out titrations using strong acids and strong alkalis only (sulfuric, hydrochloric and nitric acids only)

A
42
Q

For a given concentration of aqueous solutions, the stronger an acid, the _____ the pH

A

Lower

43
Q

As the pH decreases by one unit, what happens to the hydrogen ion concentration of the solution?

A

Increases by a factor of 10.

44
Q

Explain why weak acids have a higher pH value even if it has equal concentration to a strong acid

A

Weak acids do not completely ionise in solution
- They do not release H+ ions into the solution
- Only a small proportion of acidic molecules will ionise in their solutions
- The reaction is reversible unlike the ionisation of a strong acid, so the ions recombine to form the original molecules again

45
Q

Why are some acids called dilute and others concentrated solutions?

How are dilute solutions made?

A

A concentrated solution of a solute contains more solute in the same volume of solution

A concentrated solution is made dilute by adding water. This makes it safer and instead, an irritant

46
Q

Metal plus dilute acid:

How do potassium, sodium, lithium and calcium (PSLC) react with water and a dilute acid?

A

With water: FIZZ, GIVING OFF HYDROGEN GAS leaving an alkaline solution of a metal hydroxide
With dilute acid: EXPLODE

47
Q

How do magnesium, aluminium, zinc and iron react with water and dilute acid?

A

With water: Slow reaction
With dilute acid; fizz, giving off hydrogen gas and forming a salt

48
Q

How do tin and lead react with water and dilute acid?

A

With water: Slight reaction with steam
With dilute acid: React slowly with warm acid

49
Q

How do copper, silver and gold react with water and dilute acids?

A

They do not react with water or dilute acids

50
Q

Compare the reactions of lithium and potassium with water

A

Both will float and fizz on the surface of the water, because they are less dense than water
Both will cause a vigourous reaction
The reaction between potassium and water is more vigourous
The reaction with potassium gives out more energy and can ignite
Both produce hydrogen so bubbles would be observed
Both produce a hydroxide
They both have one electron in the outer energy level, However, the outer energy level of potassium is farther from the nucleus and lithium, so it is more easily lost. Therefore, potassium is more reactive and produces more bubbles

51
Q

What are the different ways to put metals in order of their activity?

A

Reacting the metal with water or dilute acid
Through displacement

52
Q

Whether it is worth extracting, a particular metal depends on what?

A

How easy it is to extract it from its ore
How much metal the ore contains
The changing demands for a particular metal

53
Q

Write the balanced symbol equation for the reaction between zinc oxide and dilute hydrochloric acid

A
54
Q

What is the formula of the salt, Iron(III) sulfate?

A
55
Q

Find the charges of common ions to determine the formula of salts

A
56
Q

When you react an acid with an alkali (not a base), you need to be able to tell if the acid and alkali have completely reacted. This is because no gas is given off and there is no visible insoluble base.

What could you do therefore to collect a pure, dry sample of crystals of the salt formed from an acid and alkali?

A

Carry out a titration with the indicator (acid/base one) added to see how much acid reacts completely with the alkali

Run that volume of acid into the solution of alkali again, but without the indicator

Crystallise and dry the crystals of salt as seen in the ordinary making salts practical

57
Q

Know the general formulas

A
58
Q

Why are the electrodes of electrolysis made of an inert substance?

A

So the electrodes do not react with the electrolyte, or the products made

59
Q

In electrolysis, only metals of very ____ reactivity, below ____ in the series, are deposited from their aqueous solution

A

Low

Hydrogen

60
Q

What type of bonding is present in compounds that can be electrolysed?

A

Ionic

61
Q

When extracting aluminium by electrolysis, why are the carbon anodes replaced regularly?

A

The carbon anodes are replaced regularly as they gradually burn away as oxygen reacts with the hot carbon anode forming carbon dioxide gas

Chemistry (10 decks)

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