SC15 & SC16 - Dynamic Equilibria, Calculations Involving Volumes of Gases / Chemical Cells and Fuel Cells ✓ Flashcards
SC15a - Through what do plants absorb mineral ions?
Their root hair cells
SC15a - Why must fertilisers contain soluble compounds?
Root hair cells can only absorb mineral ions that are dissolved in water
SC15a - Which three elements are featured in fertilisers?
- Nitrogen
- Potassium
- Phosphorus
SC15a - What is Ammonium Nitrate an example of?
A Nitrogenous (Nitrogen - rich) fertiliser and a source of soluble nitrogen compounds
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) + H20 (l)
NH3 (aq) + HNO3 (aq) -> NH4NO3 (aq)
SC15a - Where are the reactants for the harber process found?
- Hydrogen from natural gas
- Nitrogen from the air
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)
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)
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
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)
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)
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)
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
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
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?
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
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
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
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
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.
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
SC16a - What is a battery?
A collection of cells
SC16a - How do rechargable batteries work?
They are made out of reactants that can be reformed when electricity passes through them.
SC16a - What two elements are used in a fuel cell?
Hydrogen and Oxygen
