CHEMISTRY C4

Question 1

What does OIL RIG stand for in terms of electrons?

Answer 1

Oxidation is loss.
Reduction is gain.

Question 2

Have a look at the laminated sheet on how to prepare a dry sample of a soluble salt from an insoluble oxide or carbonate.

Answer 2

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Question 3

What is meant by a displacement reaction?

Answer 3

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

Question 4

What are some common ions and their charges?

Answer 4

Nitrate ion - N03,-
Sulphate ion - S04,2-
Hydroxide ion - OH,-
Ammonium ion - NH4,-
Carbonate ion - CO3,2-

Question 5

Acid + Alkali = ?

Answer 5

Salt + Water

Question 6

Metal + Acid = ?

Answer 6

Salt + hydrogen

Question 7

Metal oxide + Acid = ?
Metal Hydroxide + Acid = ?

Answer 7

Salt + Water

Question 8

Metal carbonate + Acid = ?

Answer 8

Salt + CO2 + Water

Question 9

When dissolved in water, which ions do acids produce?

Answer 9

Hydrogen ions.

Question 10

When dissolved in water, which ions do alkalis produce?

Answer 10

Hydroxide ions.

Question 11

What charge do elements in group 1,2,3,6,7 have?

Answer 11

Group 1 = +1
Group 2 = +2
Group 3 = +3
Group 6 = -2
Group 7 = -1

Question 12

What is the relationship between the hydrogen ion concentration and the strength of an acid?

Answer 12

Strong acids have a higher hydrogen concentration than weak acids because they completely ionise unlike weak acids which don’t.

Question 13

What is the order of reactivity series?

Answer 13

Potassium
Sodium
Calcium
Magnesium
Aluminum
Carbon
Zinc
Iron
Lead
Hydrogen
Copper
Silver
Gold
Platinum

Question 14

Why does electrolysis only work with aqueous or molten ionic compounds?

Answer 14

The ions need to be free to move and are not able to do this in solids, liquids or gases.

Question 15

Have a look at the laminated sheet and learn how to write ionic equations from symbol equations.

Answer 15

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Question 16

What happens when metals react with other substances?

Answer 16

Metal atoms lose electrons to form positive ions.

Question 17

What are some signs to show whether a metal is more reactive or not?

Answer 17

• The more vigorous its reactions are
• The more easily it loses electrons in reactions to form positive ions (cations)

Question 18

Describe and explain the observations when a small piece of lithium is placed on the surface of a big container of water. A few drops of universal indicator have been added to the water.

Answer 18

There is fizzing as the lithium reacts with the water to produce hydrogen gas. The colour of the universal indicator changes from green to purple as an alkaline solution of lithium hydroxide is produced.

Question 19

When is hydrogen produced in a reaction?

Answer 19

When a metal reacts with water or a dilute acid.

Question 20

What are native metals?

Answer 20

Metals found in the crust naturally, which are unreactive such as gold.

Question 21

What is an ore?

Answer 21

When a rock contains a high enough percentage of metal atoms to make it profitable..

Question 22

What are bases?

Answer 22

Any substance that reacts with an acid to form a salt and water only. This means that metal oxides and metal hydroxides are bases.

Question 23

What is the difference between soluble and insoluble bases?

Answer 23

Soluble bases are known as alkalis whereas insoluble bases are usually metal oxides or metal carbonates where the product won’t dissolve.

Question 24

When does neutralization occur?

Answer 24

When H+ ions are removed from a solution usually by OH- ions.

Question 25

When is a solution neutral?

Answer 25

When the concentration of OH- ions is equal to H+ ions.

Question 26

What is an electrolyte?

Answer 26

The compound on which electrolysis is carried out. They are always ionic compounds.

Question 27

During electrolysis, where do positive ions go to?

Answer 27

Positive ions move towards the negative electrode (cathode-) and gain electrons to form metallic elements or hydrogen.

Question 28

During electrolysis, where do negative ions go to?

Answer 28

Negative ions go move towards the positive electrode (anode+) and lose electrons to form non-metallic elements.

Question 29

Have a look in the orange textbook on page 73 at the electrolysis diagram.

Answer 29

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Question 30

What's formed when a metal reacts with water?

Answer 30

A metal hydroxide and hydrogen are formed.

Question 31

What are some of the pros and cons of using electrolysis to extract an element from its compound?

Answer 31

Pros: - Any element can be extracted no matter what their reactivity is Cons: - Large amounts of electrical energy is needed to carry the process out - It's expensive to do electrolysis

Question 32

Explain, with the help of a half equation, how aluminium ions are reduced during the electrolysis of aluminium oxide.

Answer 32

The half equation is: Al3+ + 3e- → Al It shows that aluminium ions gain electrons, and reduction is gain of electrons.

Question 33

Explain why all alkalis are bases, but not all bases are alkalis.

Answer 33

Alkalis are soluble bases, but only some bases are soluble in water, so these are not alkalis.

Question 34

When does a solution form?

Answer 34

When a solute dissolves in a solvent.

Question 35

The more concentrated the solution of an acid, the lower its pH will be.

Answer 35

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Question 36

A solution of 1 g/dm3 hydrochloric acid has a pH of 1.6. Predict its pH when it is diluted to 0.1 g/dm3.

Answer 36

The hydrogen ion concentration decreases by a factor of 10, so the pH increases by 1 from 1.6 to 2.6.

Question 37

Go onto C3 flashcards and learn equipment for titration practical.

Answer 37

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Question 38

Explain why a pipette is used to measure the alkali, rather than a measuring cylinder?

Answer 38

A pipette allows the same volume of alkali to be added each time, helping to make the results repeatable.

Question 39

What's the calculation for the concentration of a solution?

Answer 39

Amount of solute in mol/Volume in dm cubed

Question 40

In a titration, 25.00 cm3 of 0.200 mol/dm3 sodium hydroxide solution is exactly neutralised by 22.70 cm3 of a dilute solution of hydrochloric acid. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l) Calculate the concentration of the hydrochloric acid.

Answer 40

Volume of sodium hydroxide solution = 25.00 ÷ 1000 = 0.0250 dm3 Amount of sodium hydroxide = 0.200 × 0.0250 = 0.005 mol From the equation, 0.005 mol of NaOH reacts with 0.005 mol of HCl Volume of hydrochloric acid = 22.70 ÷ 1000 = 0.0227 dm3 Concentration of hydrochloric acid = 0.005 mol ÷ 0.0227= 0.220 mol/dm3

Question 40

What is electrolysis?

Answer 40

Electrolysis is a process in which electrical energy, from a direct current (dc) supply, breaks down electrolytes.

Question 41

True or false? the metal is produced at the cathode if it is less reactive than hydrogen and hydrogen is produced at the cathode if the metal is more reactive than hydrogen?

Answer 41

True

Question 42

True or false? Weak acids completely ionise whereas strong acids partially ionise?

Answer 42

False - Strong acids completely ionise and weak acids partially.

Question 43

How can we indicate the strength of an acid and an alkali?

Answer 43

Using universal indicator and comparing the colour of the solution with the ph scale?

Question 44

When water is ionised, which ions does it give off?

Answer 44

Hydrogen ions (H+) and hydroxide ions (OH-)

Question 45

How are volumes of acids and alkalis measured?

Answer 45

Using a burette and a pipette.