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1[GCSE Chemistry]1 > Topic 5 - Separate Chemistry 1 > Flashcards

Topic 5 - Separate Chemistry 1 Flashcards

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1
Q

Where are transition metals located?

A

In the middle of the periodic table between group 2 and group 3

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2
Q

What do all transition metals have common?

A

All have typical properties if metals.

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3
Q

Describe the properties of transition metals

A
  • Hard, strong and malleable materials that conduct electricity and heat well.
  • High melting point (except mercury which is liquid at room temperature)
  • High densities
  • They form colourful compounds
  • They make good catalysts - Iron catalyst for Haber process.
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4
Q

What does the oxidation of metals cause?

A

Corrosion

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5
Q

How can the rusting of iron be prevented?

A
  • Removing contact with oxygen
  • Removing contact with water
  • Create physical barriers such as paint or grease to stop the rust.
  • Sacrificial protection
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6
Q

What is electroplating?

A

+Electroplating involves using electrolysis to put a thin layer of a metal on the object:

  • the cathode (negatively charged electrode) is the iron or steel object
  • the anode (positively charged electrode) is the plating metal
  • the electrolyte contains ions of the plating metal
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7
Q

Why is electroplating useful?

A
  • Electroplating improves the corrosion resistance of metal objects.
  • It also improves their appearance and may be used to produce gold-plated jewelry.
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8
Q

What is sacrificial protection?

A

+Iron can be protected from rusting if it is in contact with a more reactive metal, such as zinc.
+The more reactive metal oxidises more readily than iron, so it ‘sacrifices’ itself while the iron does not rust.
+Once the sacrificial metal has corroded away, it can simply be replaced.

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9
Q

What is Galvanising?

A
  • When iron is coated in zinc, the process is called galvanising.
  • The zinc layer stops oxygen and water reaching the
    iron.
  • Zinc is more reactive than iron, so it also acts as a sacrificial metal.
  • This protection works, even if the zinc layer is scratched.
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10
Q

What are alloys?

A
  • An alloy is a mixture of two or more elements, where at least one element is a metal.
  • Many alloys are mixtures of two or more metals.
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11
Q

Why are alloys stronger than pure metals?

A

-Solid metals have a regular lattice structure. When a force is applied to a metal, layers of atoms can move past each other.
-The more difficult it is for the layers to move, the more force is needed and the stronger the metal.
Copper and zinc atoms have different sizes.
-This changes the regular lattice structure in brass, so layers of atoms cannot slide over each other so easily.
-This makes brass stronger than copper or zinc alone.

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12
Q

How are alloy steels made?

A

Iron with other metals

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13
Q

Why is iron paired with different metals to make alloy steels?

A

To suit a specific use due to their different properties. For example:
> Mild Steel - Iron + Carbon - Malleable, Ductile - Car body parts
> Tool Steel - Iron + Tungsten - Hard, Resistant to high tempereatures - Drill bits
> Stainless steel - Iron + Chromium - Hard, Resistant to rusting - Dishwasher and Washing machines.

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14
Q

How is the properties of aluminium related to its use?

A
  • Aluminium foil is used to wrap food and store it because it doesn’t react to the substances in the food.
  • It is malleable so it can be wrapped around the food.
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15
Q

How is the properties of magnalium related to its use?

A

Has low density, is strong and is malleable so it is used for aircraft parts.

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16
Q

How is the properties of copper and brass related to its use?

A
  • Copper and brass resist corrosion and are good electrical conductors.
  • Copper is a better conductor than brass, and it is used in electrical wiring.
  • Brass is stronger than copper, so it is used for the pins in electrical plugs.
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17
Q

How does the properties of gold relate to its use?

A
  • Gold is a very soft and malleable metal. It is also very unreactive, so it resists corrosion and stays shiny.
  • The gold used for jewellery is gold alloyed with other metals, often copper.
  • This makes the jewellery much stronger while keeping its ability to stay shiny.
18
Q

What is the theoretical yield and how is it calculated?

A

A theoretical yield is the maximum possible mass of a product that can be made in a chemical reaction.

It can be calculated from:

  • the balanced equation,
  • the mass and relative formula mass of the limiting reactant, and
  • the relative formula mass of the product
19
Q

What is the actual yield?

A

An actual yield is the mass of a product actually obtained from the reaction. It is usually less than the theoretical yield. The reasons for this include:

  • incomplete reactions, in which some of the reactants do not react to form the product
  • practical losses during the experiment, such as during pouring or filtering
  • side reactions (unwanted reactions that compete with the desired reaction)
20
Q

How is the percentage yield calculated?

A

(Actual yield ÷ Theoretical yield) x 100

21
Q

What is the atom economy?

A

The atom economy of a reaction is a measure of how many reactant atoms form a desired product.

22
Q

How do calculate atom economy?

A

(Total Mr of the desired product ÷ Total Mr of all reactants) x 100

23
Q

How do you convert from cm3 to dm3?

A

divide by 1000

24
Q

How do you work out the concentration of a solution in mol dm-3?

A

Number of moles ÷ Volume in dm3

25
Q

How do you convert from mol dm-3 to g dm-3?

A

Multiply by the Mr

26
Q

How do you work out a titration calculation?

A
  • Find the number of moles of the solution with info
  • Write out the equation for the reaction
  • Work out the n.o of moles of the unknown substance
  • Work out the concentration of the unknown substance
27
Q

How do you use Avogadro’s law to work the volume of gase?

A

Volume of gas = Number of moles x 24

28
Q

4.6 g of sodium reacts completely with excess water:

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

Calculate the volume of hydrogen produced. (Ar of Na = 23, molar volume = 24 dm3)

A

Step 1 - Calculate the amount of sodium

Amount in mol = Mass in g ÷ Ar

Amount in mol = 4.6 ÷ 23

Amount of sodium = 0.20 mol

Step 2 - Find the amount of hydrogen

From the balanced equation, the mole ratio Na:H2 is 2:1

Therefore 0.20 mol of Na produces 0.20 ÷ 2 = 0.10 mol of H2

Step 3 - Calculate the volume of hydrogen

Volume = amount in mol × molar volume

Volume = 0.10 × 24

= 2.4 dm3

29
Q

Lithium hydroxide absorbs carbon dioxide from the air:

2LiOH(s) + CO2(g) → Li2CO3(s) + H2O(l)

Calculate the mass of lithium hydroxide needed to absorb 12 dm3 of carbon dioxide. (Mr of LiOH = 24, molar volume = 24 dm3)

A

Step 1 - Calculate the amount of carbon dioxide

Amount in mol = volume ÷ molar volume

Amount in mol = 12 ÷ 24

= 0.50 mol

Step 2 - Find the amount of lithium hydroxide

From the balanced equation, the mole ratio LiOH:CO2 is 2:1

Therefore 0.50 mol of CO2 is absorbed by (0.50 × 2) = 1.0 mol of LiOH

Step 3 - Calculate the mass of lithium hydroxide

Mass in g = Mr × amount in mol

Mass = 24 × 1.0

= 24 g

30
Q

What is molar volume of any gas at room temperature and pressure?

A

24dm-3

31
Q

What is the Haber process?

A

A reversible reaction between nitrogen and hydrogen to form ammonia

32
Q

What do fertilisers contain and what do they do?

A

Fertilisers may contain nitrogen, phosphorus and potassium compounds to promote plant growth.

33
Q

How does ammonia react to produce a salt used as a fertiliser.

A

Ammonium nitrate, NH4NO3, is a salt used as a fertiliser. It can be manufactured by reacting ammonia solution with nitric acid:

Ammonia + nitric acid → ammonium nitrate

NH3(aq) + HNO3(aq) → NH4NO3(aq)

34
Q

How is ammonium sulfate made on a small scale in a lab?

A

Ammonium sulfate can be made in the lab using dilute ammonia solution and dilute sulfuric acid in a titration
Ammonia + sulfuric acid → ammonium sulfate
2NH3(aq) + H2SO4(aq) → (NH4)2SO4(aq)

Method:

  1. Put some dilute sulfuric acid into a beaker.
  2. Add a few drops of methyl orange indicator.
  3. Add dilute ammonia solution drop by drop, stirring in between.
  4. Continue step 3 until the colour permanently changes from red to yellow.
  5. Add a few more drops of dilute ammonia solution.
  6. Pour the reaction mixture into an evaporating basin, and heat carefully over a boiling water bath.
  7. Stop heating before all the water has evaporated. Leave aside for crystals to form. More on crystallisation can be found here.
  8. Pour away excess water and leave the crystals to dry in a warm oven (or pat dry with filter paper).
35
Q

How is ammonium sulfate made on a large scale in industry?

A
  • The industrial production has several stages as the ammonia and sulfuric acid have to be made from their raw materials.
  • Ammonia is made from the Haber process and sulfuric acid is produced using a process called the contact process.
  • One industrial method uses a reaction chamber filled with ammonia gas.
  • Sulfuric acid is sprayed into the reaction chamber, where it reacts with the ammonia sulfate to produce ammonium sulfate powder.
36
Q

Why is the lab method not used in industry to make ammonium sulfate?

A

Impractical to use burettes and steam baths to make large quantities and using crystallisation to get solid ammonium sulfate is too slow.

37
Q

What is a fuel cell?

A

An electrical cell that’s supplied with fuel and oxygen and uses energy from the reaction between them to produce electrical energy efficiently

38
Q

What do chemical cells do?

A

They produce a voltage across the cell, until all of one of the reactants have been used up.

39
Q

Describe Hydrogen-fuel cells

A

They use hydrogen as fuel. You can produce a voltage by reacting oxygen and hydrogen together and it doesn’t produce any bad pollutants but only clean water.
2H2 + O2 = 2H2O

40
Q

What are the advantages of fuel cells?

A
  • Electricity is directly generated from the reaction (no turbines)
  • Little stages to generate electricity, fewer places to lose energy as heat
  • No moving parts so energy isn’t lost through friction
  • No pollutants: No greenhouse gases, nitrogen oxides, sulfur dioxide, carbon monoxide so it would reduce air pollution.
41
Q

What are the disadvantages of hydrogen fuel cells?

A
  • Hydrogen is gas so it takes up more space than liquid fuels like petrol
  • It very explosive so it is difficult to store safely
  • The hydrogen fuel is often made either from hydrocarbons or by electrolysis of water, which uses electricity.

1[GCSE Chemistry]1 (35 decks)

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