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chemistry GCSE > C5-Chemical Changes > Flashcards

C5-Chemical Changes Flashcards

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1
Q

How is the reactivity of metals decided

A
  • When metals react they lose electrons and form positive ions
  • The reactivity of a metal is decided by how easy or hard it is for that metal to lose electrons
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2
Q

How are unreactive metals extracted

A

Unreactive metals are extracted in their native state in the ground

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3
Q

How are more reactive metals extracted found in the ground

A

More reactive metals are found in the ground as metal oxides as they have reacted with oxygen in the ground

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4
Q

How are these more reactive metals extracted

A

These more reactive metals are extracted by a more reactive element dispacing it from its compound

This is usually carbon as other elements are more expensive so not used. If the metal is more reactive than carbon it is extracted by electrolysis

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5
Q

What is an example of a reaction for the extraction of a more reactive metal

A

Iron oxide + carbon —> carbon dioxide + iron

The iron is reduced
F2+ + 2e- = Fe
Carbon has been oxidised
C+ 2e-=C2+

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6
Q

What is oxidation in terms of electrons

A

Oxidation is loss of electrons

E.g if an atom turns into an ion

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7
Q

What is reduction in terms of electrons

A

Reduction is gain of electrons

For example if an ion turns into an atom

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8
Q

What do all acids contain

A

All acids contain hydrogen

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9
Q

How do metals react with acid

A

Metals higher than hydrogen in the reactivity series displace hydrogen when they react with an acid to form a salt of their metal

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10
Q

What is the equation for the reaction of acids and metals

A

Metal + acid —-> salt + hydrogen

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11
Q

What type of salt does hydrochloric acid form

A

Hydrochloric acid forms salts ending in chloride

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12
Q

What type of salt does sulphuric acid form

A

Sulphuric acid forms acids ending in sulphate

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13
Q

How is the speed of the reactions with the metals decided

A

The further away a metal is on the reactivity series from hydrogen , the more fast it reacts

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14
Q

What types of ions do acids produce in an aqueous solution

A

Acids produce hydrogen ions in aqueous solutions

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15
Q

What are bases

A

Bases are chemicals that can neutralise an acid to produce a salt and water

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16
Q

What are soluble bases called

A

Soluble bases are called alkali’s

17
Q

What is the PH scale and how can it be measured

A

The PH scale is a scale that tells the acidity or alkalinity of acids

It can be measured using universal indicator or a PH probe

Alkalis have a PH of 8-14

Neutral solutions have a PH of 7

Acids have a PH of 0-7

18
Q

What is the equation for a neutralisation reaction

A

H+ + OH- = H20

The OH is produced by the alkali and the hydrogen is produced by the acid.

The solution produced has a Ph of 7 and is neutral

19
Q

What happens to a strong acid in an aqueous solution

A

A strong acid in an aqueous solution fully ionises and the reaction is not reversible

-Strong acids have a lower PH than weaker acids

20
Q

What happens to weaker acids in aqueous solutions

A

Weaker acids only partially ionise in aqueous solutions and the reaction is reversible

21
Q

What happens to the hydrogen ions in a solution as the PH decreases

A

For every PH decrease the amount of hydrogen ions increases 10 times

-Strong acids will have lower PH’s as the atoms are fully ionised so their are more hydrogen ions

22
Q

How does the concentration of an acid affect the PH

A

The concentration of an acid tells us the amount of acid in a given volume of solution. A dilute acid will have less molecules of acid for a given volume of solution than a comcentrated acid .

(You can have a dilute strong acid that is not concentrated)

PH will decrease with increasing concentration

23
Q

What happens when a base or alkali reacts with an acid

A

When a base or alkali reacts with an acid it produces a salt and water

24
Q

What sort of ions does the salt from this reaction contain

A

The salt from this reaction contains positive ions from the base and negative ions from the acid

Hydrochloric acid —-> chlorides
Nitric acid —-> nitrates
Sulfuric acid —-> sulphates

25
Q

What happens when metal carbonates react with acids

A

When metal carbonates react with acid they produce a salt , water and carbon dioxide

Metal carbonate + acid —> salt + water + carbon dioxide

26
Q

What colours do indicators turn depending on what type of solution is being tested

A

If an acid is present the indicator will turn red

If an alkali is present the indicator will turn towards purple

27
Q

Describe the steps in a titration reaction

A
  • Use a pipette to transfer 25cm3 of sodium hydroxide solution into a conical flask( make sure to let all of the solution drain out of the pipette)
  • Add 5 drops of indicator to the solution to the alkali in the conical flask
  • Place the conical flask on a white tile so you can see the colour change more clearly
  • Fill a burette with an acid and add it to the alkali until the solution is neutral. When you start to see a colour change add the acid to the solution drop by drop until the solution is neutral
  • Record the final volume of acid in the burette and use the initial volume to work out the amount of acid used in the neutralisation
  • Repeat the experiment until you get two readings within 0.1cm3 of each other
28
Q

Describe the steps in Making a soluble salt

A

Start with a fixed volume of dilute sulfuric acid. This is the limiting reactant

Gently heat the acid until almost boiling

Use a spatula to add small amounts of copper oxide to the acid

The copper oxide will react and seem to disappear (solution will be blue as that is colour of copper sulphate )

Stop adding copper oxide when the copper oxide powder stays after stirring . At this point the reaction has stopped

Use filtration to filter out the excess copper oxide

Place the solution in an evaporating basin and heat gently over boiling water until roughly half the solution remains

Leave the copper sulphate for 24 hours in a cool place so copper sulphate crystals can form

Scrape the crystals onto a paper towel and leave them to dry

29
Q

How can you measure the reactivity of metals

A
  • Add all the metals to acid
  • Measure the temperature change of the reaction between the acid and the metal over a set period
  • The greater the temperature change the more reactive the metal

Keep the same mass and surface area of metal

chemistry GCSE (17 decks)

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