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

1
Q

SC15a - Through what do plants absorb mineral ions?

A

Their root hair cells

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2
Q

SC15a - Why must fertilisers contain soluble compounds?

A

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

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3
Q

SC15a - Which three elements are featured in fertilisers?

A
  • Nitrogen
  • Potassium
  • Phosphorus
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4
Q

SC15a - What is Ammonium Nitrate an example of?

A

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

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5
Q

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

A
  • Ammonium is created through the Haber 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)
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6
Q

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

A
  • Hydrogen from natural gas
  • Nitrogen from the air
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7
Q

SC15a - Describe a laboratory preparation of ammonium sulfate.

  • scale of production
  • starting materials
  • stages
  • type of process
  • maintenance
A
  • scale of production - small
  • starting materials - ammonia solution and dilute sulfuric acid
  • stages - titration followed by crystallisation
  • type of process - batch process
  • maintenance -apparatus must be cleaned regularly - difficult to automate
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8
Q

SC15a - Describe a factory preparation of ammonium sulfate.

  • scale of production
  • starting materials
  • stages
  • type of process
  • maintenance
A
  • scale of production - large
  • starting materials - raw materials for making ammonia and sulfuric acid
  • stages - several stages
  • type of process - continuous
  • maintenance - only stopped rarely to maintain and clean equipment
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9
Q

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

A
  • Sulfur and air are reacted to form sulfur trioxide
  • Sulfur trioxide is reacted with water to from Sulfuric acid
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10
Q

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

A
  • Equilibrium shifts in the endothermic direction
  • Rate of attainment increased as the particles have more energy causing more frequent collisions.
  • (All are opposite if temperature is decreased)
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11
Q

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

A
  • 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)
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12
Q

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

A
  • 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)
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13
Q

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

A
  • 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
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14
Q

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

A
  • 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
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15
Q

SC15b - What were the disadvantages of the Birkeland-Eyde process?

A
  • It was inefficient only producing a yield of 4% nitric acid
  • It cost lots as it took up huge amounts of electricity
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16
Q

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

A

The Ostwald process:

  • Ammonia + Oxygen ⇌ Nitrogen monoxide + Water
  • Nitrogen Monoxide + Oxygen ⇌ Nitrogen dioxide
  • Nitrogen Dioxide + Oxygen + Water → Nitric Acid
17
Q

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

A
  • Availability of raw materials and energy supplies
  • Rate of reaction and equilibrium position
  • Atom economy, yield and usefulness of the by-products
18
Q

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

A

220° and 4atm with a hot platinum catalyst

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

19
Q

SC16a - What are the components in a chemical cell?

A
  • 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
Q

SC16a - How can the strength of a chemical cell be altered?

A
  • 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
Q

SC16a - Why may a battery go flat?

A

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

22
Q

SC16a - What is a battery?

A

A collection of cells

23
Q

SC16a - How do rechargable batteries work?

A

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

24
Q

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

A

Hydrogen and Oxygen

25
Q

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

A

Electrodes

26
Q

SC16a - What process do fuel cells mimick?

A

Photosynthesis

27
Q

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

A
  • The 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
Q

SC16a - What are the pros and cons of hydrogen-oygen fuel cells?

A

Pros:

  • Quiter and need less maintenance in a petrol or diesel engine
  • 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