Separate chemistry

Question 1

What are the properties of transition metals

Answer 1

• High melting point due to electrostatic forces between positive metal ions and sea of electrons
• High density
• Form coloured compounds
• Useful as catalysts

Question 2

What causes corrosion

Answer 2

Water and oxygen

Question 3

How does sacrificial protection prevent the rusting of metal

Answer 3

Using a more reactive metal to coat a less reactive metal causing it to corrode instead

Question 4

How can water and oxygen be excluded (not able to affect) from a metal

Answer 4

• Painting
• Coating with plastic
• Using oil or grease

Question 5

How does electroplating improve the appearance and/or the resistance to corrosion of metal objects

Answer 5

• Acts as a barrier to exclude oxygen and water
• Improves appearance if electroplating with an unreactive metal

Question 6

Why does converting pure metals into alloys increase the strength of the product

Answer 6

Pure metals = have positive ions the same size and in a regular arrangement so layers easily side over each other
Alloy = have positive ions of different metals which have different sized ions so layers can’t slide as easily

Question 7

Why is iron alloyed with other metals to produce alloy steels

Answer 7

So they can be designed to fit a specific use

Question 8

What are low-carbon steels used for and why

Answer 8

Sheeting as they are malleable and easily shaped

Question 9

What are high carbon steels used for and why

Answer 9

Cutting tools since they are hard

Question 10

What is the alloy of chromium and nickel used for and why

Answer 10

Stainless steels (used for cutlery) as they are resistant to corrosion

Question 11

How is aluminium useful for its property

Answer 11

has a low density therefore used for aircraft

Question 12

How is copper useful for its property

Answer 12

Good electrical conductor therefore used in cables

Question 13

How is gold useful for its property

Answer 13

Good resistance to corrosion therefore used in jewlery

Question 14

How is magnalium (aluminium + magnesium) useful for its property

Answer 14

Low density therefore good for cars and planes

Question 15

How is Brass (copper + zinc) useful for its property

Answer 15

Hard and resistant to corrosion therefore used in coins

Question 16

How do you work out concentration of a solution (2 ways)

Answer 16

• concentration (g/dm^3) = mass (g) ÷ volume (dm^3)
• concentration (mol dm^-3) = number of moles ÷ volume of solution (dm^3)

Question 17

What are the two ways of showing concentration

Answer 17

g/dm3 or mol/dm3

Question 18

How do you convert g/dm3 to mol/dm3

Answer 18

divide by the relative formula mass/molar mass

Question 19

How do you convert from mol/dm3 to g/dm3

Answer 19

multiply by the relative formula mass

Question 20

How do you convert a cubic centimetre into a cubic decimetre

Answer 20

divide by 1000

Question 21

How do you convert a cubic decimetre into a cubic centimetre

Answer 21

multiply by 1000

Question 22

How do you carry out an acid-alkaline practical

Answer 22

• add acid to burette using a funnel, record the volume in the burette to
  start
• add known volume of alkali to a conical flask and add some indicator
• place conical flask on white tile (so you can see colour change clearly)
• add acid to alkali and swirl until you reach the end point
• calculate how much acid has been added (titre)
• repeat until you get concordant titres

Question 23

How do you work out percentage yield

Answer 23

(actual yield / theoretical yield) x 100

Question 24

What are some causes for the actual yield being smaller than theoretical yield

Answer 24

• incomplete reactions
• side reactions
• reversibile reaction

Question 25

What is atom economy

Answer 25

Amount of useful products gained from the reactances

Question 26

How do you work out atom economy

Answer 26

atom economy = (Mr of desired product from reaction / sum of Mr of all reactants) x 100

Question 27

Explain why a particular reaction pathway is chosen to produce a specified product

Answer 27

To produce a: * a high atom economy * a high yield * at faster rate

Question 28

What is molar volume in cm^3 and dm^3)

Answer 28

cm^3 = 24,000 dm^3 = 24

Question 29

How do you calculate the volume of a gas

Answer 29

Volume = amount in mol × molar volume

Question 30

What is Avogadro's law

Answer 30

One mole of a substance contains 6.02 x 10^23 particles

Question 31

How is equilibrium achieved at a faster rate

Answer 31

* Higher temperature is used * A higher pressure * A higher concentration is used * A catalyst is used

Question 32

How does temperature affect equilibrium

Answer 32

Increase of temperature: equilibrium will shift to favour the reaction which will reduce the temperature. (endothermic) Decrease of temperature: equilibrium will shift to favour the reaction which will increase the temperature. (exothermic)

Question 33

How does pressure affect equilibrium

Answer 33

Increase of pressure: reaction favours the side with a smaller molar volume Decrease of pressure: reaction favours the side with a larger molar volume

Question 34

What 3 compounds are used in fertilisers to increase agriculture

Answer 34

* Nitrogen * Phosphorus * Potassium

Question 35

How does ammonia react with nitric acid to produce a salt that is used as a fertiliser

Answer 35

ammonia + nitric acid → ammonium nitrate (NH3 + HNO3 → NH4NO3)

Question 36

What is the equation for forming ammonium nitrate

Answer 36

(NH3 + HNO3 → NH4NO3)

Question 37

Describe the process of making ammonia sulphate in a lab

Answer 37

* reactants: ammonia solution and dilute sulfuric acid (bought from chemical manufacturers) * SMALL scale * only involves a few stages (titration then crystallisation)

Question 38

Describe the process of making ammonia sulphate in an industry

Answer 38

* Ammonia: natural gas, air, water * Sulfuric acid: sulphur, air, water * LARGE scale ○ Many stages required (need to make ammonia and sulfuric acid, react accurate volumes then evaporate)

Question 39

How does a catalyst affect equilibrium

Answer 39

* doesn't shift the position of equilibrium * allows the equilibrium to be established faster * less heat is needed

Question 40

what happens if you increase the concentration of a reactant?

Answer 40

increasing the concentration of a reactant system makes more products to balance it out

Question 41

NA

Answer 41

NA

Question 42

When do chemical reactions stop

Answer 42

Chemical reactions stop when one of the reactants has been used up

Question 43

What is the reaction in a hydrogen fuel cell

Answer 43

Hydrogen + Oxygen → Water 2H2 + O2 → 2H2O

Question 44

What are the positives of using fuel cells

Answer 44

* produce only water as a waste * Keeps producing fuel if being supplied

Question 45

What are the negatives of using fuel cells

Answer 45

* difficult to transport/store hydrogen so aren’t suitable for portable devices * expensive to make