SC15 & SC16 - Dynamic Equilibria, Calculations Involving Volumes of Gases / Chemical Cells and Fuel Cells ✓ Flashcards Preview

Edexcel GCSE Chemistry COPY > SC15 & SC16 - Dynamic Equilibria, Calculations Involving Volumes of Gases / Chemical Cells and Fuel Cells ✓ > Flashcards

Flashcards in SC15 & SC16 - Dynamic Equilibria, Calculations Involving Volumes of Gases / Chemical Cells and Fuel Cells ✓ Deck (28)
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1

SC15a - Through what do plants absorb mineral ions?

Their root hair cells

2

SC15a - Why must fertilisers contain soluble compounds?

Root hair cells can only absorb mineral ions that are dissolved in water

3

SC15a - Which three elements are featured in fertilisers?

  • Nitrogen
  • Potassium
  • Phosphorus

4

SC15a - What is Ammonium Nitrate an example of?

A Nitrogenous (Nitrogen-rich) fertiliser and a source of soluble nitrogen compounds

5

SC15a - How is ammonium nitrate manufactured and how are the materials gathered?

  • Ammonium is created through the harber process.
  • Then some ammonia is reacted with oxygen to give nitric acid and oxygen.
  • This nitric acid is reacted with some ammonium solution.
  • This creates ammonium nitrate:
  • NH3 (g) + 2O2 (g) → HNO3 (aq) + H2O (l)
  • NH3 (aq) + HNO3 (aq) →NH4NO3 (aq)

6

SC15a - Where are the reactants for the harber process found?

  • Hydrogen from natural gas
  • Nitrogen from the air

7

SC15a - Describe a laboratory preparation of ammonium sulfate.

  • Small scale
  • Batch process (only bit by bit)
  • Ammonium solution and dilute sulfuric acid
  • Titration followed by crystallisation
  • Small amount made; equipment is cleaned; repeat
  • Requires frequent maintenance (Hard to automate)

8

SC15a - Describe a factory preparation of ammonium sulfate.

  • Large scale
  • Continuous process
  • Raw materials for Ammonia and Sulfuric acid
  • Several stages
  • Large amount made, rarely cleaned
  • Little maintenance required (Easy to automate)

9

SC15a - How is sulfuric acid formed for factory preparation of ammonium sulfate?

  • Sulfur and air are reacted to form sulfur trioxide
  • Sulfur trioxide is reacted with water to from Sulfuric acid

10

SC15b - How does an increase in temperature affect the position of equilibrium and rate of attainment?

  • Exothermic: Equilibrium shifts to left
  • Endothermic: Equilibrium shifts to right
  • Rate of attainment increased as the particles have more energy causing more frequent collisions.
  • (All are opposite if temperature is decreased)

11

SC15b - How does an increase in pressure affect the position of equilibrium and rate of attainment?

  • Equilibrium favors the side with fewer molecules
  • Rate of attainment is increased as the same amount of particles in a smaller space causes more frequent collisions
  • (Opposite if pressure is decreased)

12

SC15b - How does an increase in concentration of the reactant affect the position of equilibrium and rate of attainment?

  • Equilibrium shifts towards the products side.
  • Rate of attaimment is increased as there are more particles in the same space and so there are more frequent collisions
  • (Opposite if concentration is decreased)

13

SC15b - How does a catalyst affect the position of equilibrium and rate of attainment?

  • Position of equilibrium is unaffected as it effects both sides equally
  • Rate of attainment is increased as the catalyst increases the rate of reaction without being used up

14

SC15b - What natural occurance did the birkeland - eyde process mimick and how was this used to produce Nitric acid?

  • Lightning.
  • An electric arc was created between two electrodes causing nitrogen to react with oxygen in the air forming nitrogen monoxide.
  • This was then further reacted with oxygen to form nitrogen dioxide and then dissolved in water to form nitric acid

15

SC15b - Why was the Birkeland-Eyde process bad?

  • It was inefficient only producing a yield of 4% nitric acid
  • It cost lots as it took up huge amounts of electricity?

16

SC15b - What process do we now use to obtain Nitric Acid and how does it work?

The otswald process:

  • Ammonia + Oxygen ⇌ Nitrogen monoxide + Water
  • Nitrogen Monoxide + Oxygen ⇌ Nitrogen dioxide
  • Nitrogen Dioxide + Oxygen + Water → Nitric Acid

17

SC15b - What is taken into consideration when choosing reaction pathways?

  • Availability of raw materials and energy supplies
  • Rate of reaction and equilibrium position
  • Atom economy, yield and usefulness of the by-products

18

SC15b - What are the conditions for stage one of the Otswald Process?

220° and 4atm with a hot platinum catalyst

(Ammonia to Nitrogen monoxide is exothermic and there are more molecules on the right)

19

SC16a - What are the components in a chemical cell?

  • Two different metals each dipped in a solution of one of their own salts
  • A salt (or ion) bridge to allow the ions to pass from one solution to another and complete the circuit

20

SC16a - How is a potential difference created in a chemical cell and how can its strength be altered?

  • Metals push their electrons away with a certain force.
  • The more reactive metal pushes its electrons away to the lesser reactive one which is forced to accept it.
  • This flow of electrons creates a potential difference.
  • Metals that have a greater difference in reactivity will create a larger potential difference.
  • This will also create a greater current as there are more electrons flowing past one point over a given time.

21

SC16a - Why may a battery go flat?

One of its reactants have been completely used up and so there are no more elctrons flowing past

22

SC16a - What is a battery?

A collection of cells

23

SC16a - How do rechargable batteries work?

They are made out of reactants that can be reformed when electricity passes through them.

24

SC16a - What two elements are used in a fuel cell?

Hydrogen and Oxygen

25

SC16a - What is used at both sides of the fuell cell to create ions?

Electrodes

26

SC16a - What process do fuel cells mimick?

Photosynthesis

27

SC16a - Explain how hydrogen atoms provide electricity in a fuel cell.

  • They hydrgoen fuel enters the fuel cell.
  • Here it reaches an electrode and becomes a hydrogen ion losing its electron.
  • The electrons move through the circuit providing a current in the circuit.
  • The hydrogen ion passes through a water membrane to meet back with an electron and react with
  • Oxygen atoms to form water.

28

SC16a - What are the pros and cons of hydrogen-oygen fuel cells being used in cars?

Pros:

  • Quiter and need less maintenance
  • The cell itself doesn't release greenhouse gases

Cons:

  • The production of hydrogen may release greenhouse gases and also use up fossil fuels.
  • Hydrogen needs to be stored carefully as it can explode