Triple & Further Science: Chemistry (III) Flashcards Preview

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Flashcards in Triple & Further Science: Chemistry (III) Deck (60)
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1

What was the early periodic table based on?

Their physical / chemical properties and their atomic mass

2

What did Newland set out for his periodic table?

Newland’s law of octaves – every 8th element had similar properties

3

What did Mendeleev do with his periodic table?

Mendeleev left gaps and predicted new elements – he put known ones in order of atomic mass

4

Why were the gaps so important in Mendeleev’s periodic table?

The gaps predicted the properties of undiscovered elements

5

What is the modern periodic table based on?

Electron structure – this can predict the element’s chemical properties (group number is equal to the number of electrons in the outer shell)

6

What are the alkali metals and what properties do they have?

Alkali metals are group 1 elements – they become more reactive down the group (outer e- further from nucleus) and have lower melting and boiling points

 

They also have a low density (Li, Na and K less dense than water)

7

How many electrons in the outer shell are present in group 1 elements (alkali metals)?

1 electron – making them very reactive and forming ionic compounds with non-metals (which produce white compounds that dissolve in water forming colourless solutions)

8

How do the alkali metals react when placed in water?

They react vigorously producing hydrogen gas and form hydroxides that dissolve producing alkaline solutions

 

2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)

 

2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)

9

What are the group 7 elements known as and what are their properties?

Halogens – they are non-metals with 7 outer electrons and become less reactive (as it is harder to gain an e- as the outer shell is further from the nucleus) and have higher melting and boiling points

10

What colour vapours do the halogens fluorine, chlorine, bromine and iodine form?

Fluorine = yellow gas; chlorine = green gas; bromine = red-brown liquid; iodine = dark grey solid / purple vapour

11

What do the halogens form with metals?

Ionic bonds with metals (1- ions) called halides

12

What will more reactive halogens do too less reactive ones?

A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt

 

Cl2 (g) + 2Kl (aq) → I2 (aq) + 2KCl (aq)

 

Cl2 (g) + 2KBr (aq) → Br2 (aq) + 2KCl (aq)

13

What are the transition elements?

Transition elements are positioned between group 2 and 3 and are good conductors of heat and electricity; dense, strong, and shiny

14

What are the properties of the transition metals?

Transition metals often have more than one ion (e.g. Fe+2, Fe+3), form colourful compounds and make good catalysts

15

What is hard water and what does it make?

Hard water makes scum and scale (instead of lather with soap) due to calcium and magnesium ions dissolved in the water (scale is mostly calcium carbonate which is a thermal insulator and making heating elements less efficient)

 

*But calcium ions are good for teeth / bones and it is suggested minerals in hard water reduce heart disease

16

What ions cause hardness in water?

Calcium ions (Ca+2) and Magnesium ions (Mg+2)

17

How is hard water made soft?

The calcium and magnesium ions are removed

18

What is temporary / permanent hardness caused by and how is this removed?

Temporary hardness is caused by HCO3- and can be removed by boiling (HCO3- decomposes to insoluble CO3)

 

Permanent hardness can only be softened using washing soda (Na2CO3) where the carbonate ions react with the Ca+2 and Mg+2 ions

19

How can the hardness of water be compared?

Titrations – soap solution can be added to the water until a lasting lather was created

20

How can water quality be improved?

Filtration (removal of materials) and chemicals added to kill microbes

21

Why are chlorine / fluoride added to water and what problems may these cause?

Fluoride is added to drinking water to help reduce tooth decay and chlorine is added to prevent disease

 

Some studies have linked fluoride and chlorine to increased cancer

22

What is a reversible reaction?

A reversible reaction is one where the products of the reaction can themselves react to produce the original reactants

23

What happens if a reversible reaction takes place in a closed system?

Equilibrium is reached – the amounts of reactants and products will reach a balance

24

How can the position of the equilibrium in a reversible reaction be changed?

The temperature and pressure can be changed

25

How does temperature affect and exothermic and endothermic reaction?

All reactions are exothermic reaction in one direction and endothermic in the other

 

  • Temp. raise causes endothermic reaction to increase (use up the extra heat)
  • Temp. fall causes exothermic reaction to increase (give out more heat)

26

How does pressure affect an exothermic and endothermic reaction?

Many reactions have a greater volume on one side (either reactants or products)

 

  • Pressure raise encourages the reaction will produces less volume
  • Pressure fall encourages the reaction will produces more volume

27

What does a catalyst do to the equilibrium position?

Catalysts do not change the equilibrium position – they speed up both the forward and reverse reactions by the same amount

28

What is the Haber process?

Ammonia production

 

Nitrogen + Hydrogen Ammonia

 

N2 (g) + 3H2 (g) 2NH3 (g)

29

What conditions are needed for the Haber process?

Nitrogen from air and hydrogen from natural gas at 200 atmosphere pressure and 450oC with an iron catalyst

30

How does the Haber process recycle its ‘waste’?