Aqa A2 Chem5 - Periodicity and redox equilibria

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  • Created by: Aqeel
  • Created on: 11-05-13 00:39
Write an equation to show the reaction of magnesium with water.
Mg + 2H2O -------> Mg(OH)2 + H2
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Explain why magnesium reacts less vigorously with water than sodium.
Magnesium loses two electrons to form an Mg²+ ion but sodium only loses one electron to form an Na+ ion. It takes less energy for sodium to lose one electron than it does for magnesium to lose two. So more energy is needed for magnesium to react
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Sodium and magnesium both react vigorously with oxygen to produce oxides. These oxides are structurally similar but they have very different melting temperatures. Write an equation to show the reaction of sodium with oxygen.
2Na + 0.5O2 ------> Na2O
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What colour is the flame produced when sodium is burnt in air?
Yellow
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Describe the structure of sodium oxide and magnesium oxide
Both form giant ionic lattices, with strong ionic bonds between each ion
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State which oxide has the higher melting point and explain why their melting temperatures are different.
MgO has a higher melting temperature. Magnesium forms Mg²+ ions, which attract O²¯ ions more strongly than the Na+ ions in Na2O, so the ionic bonds in MgO are stronger and more heat energy is required to break the bonds.
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Non - metal Period 3 elements uch as silicon, phosphorus and sulfur also react with oxygen to produce oxides. Explain why sulfur dioxide has a relatively low melting point.
Sulfur dioxide has a simple molecular structure. Only weak intermolecular forces like van der waals hold the molecules together. Little energy is needed to overcome these forces.
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Explain why the melting point of silicon dioxide is unusually high.
Silicon dioxide has a giant macromolecular structure, with strong covalent bonds holding the molecules together. Lots of energy is required to break these bonds
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The period 3 oxides react differently with water. Write equations showing the reactions of magnesium oxide and sulfur dioxide with water. Give the approximate PHs of the solutions formed
MgO + H2O -------> Mg(OH)2 (PH - 9/10) SO2 + H2O ------> H2SO3 (PH - 0-2)
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Name one period 3 oxide that is insoluble in water.
Aluminium oxide/ Silicon dioxide
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State which period 3 oxide is amphoteric
Aluminium oxide
11 of 17
Write two equations showing Aluminium oxide reacting with an acid and a base
Al2O3 + 3H2SO4 -----> Al2(SO4)3 + 3H2O
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The electrode itself is made of platinum. Suggest why platinum is a suitable metal to use for this purpose
Platinum is inert
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Lead - acid batteries are a type of rechargeable battery commonly used to operate the starter motors of cars. Explain why rechargeable batteries can be recharged
The reactions that occur within them can be reversed if a current is supplied to force the electrons to flow in the opposite direction around the circuit.
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Discuss the advantages and disvantages of using rechargable batteries instead of standard non- rechargable batteries
Advantages : They dont have to be replaced when they run out so are cheaper in the long run/supply more power than non-rechargables/ less waste because they can be reused. Disadvantages : more expensive/ dont work for long/ contain toxic metals
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Explain why electrodes of a hydrogen - oxygen fuel cell are typically made by coating a ceramic material with a thin layer of platinum, rather than using solid platinum rods.
It is cheaper and it provides a larger surface area so the reaction goes faster.
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Give two advantages of using hydrogen - oxygen fuel cells over conventional batteries
They don't need electricity recharging, the only waste product is water and also they dont produce CO₂ emissions.
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Other cards in this set

Card 2

Front

Explain why magnesium reacts less vigorously with water than sodium.

Back

Magnesium loses two electrons to form an Mg²+ ion but sodium only loses one electron to form an Na+ ion. It takes less energy for sodium to lose one electron than it does for magnesium to lose two. So more energy is needed for magnesium to react

Card 3

Front

Sodium and magnesium both react vigorously with oxygen to produce oxides. These oxides are structurally similar but they have very different melting temperatures. Write an equation to show the reaction of sodium with oxygen.

Back

Preview of the front of card 3

Card 4

Front

What colour is the flame produced when sodium is burnt in air?

Back

Preview of the front of card 4

Card 5

Front

Describe the structure of sodium oxide and magnesium oxide

Back

Preview of the front of card 5
View more cards

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