Equilibrium

What is theoretical yield?

The maximum mass of product that can be formed from the reactant. This is calculated from the balanced equation.

What is the actual yield?

The amount of yield actually obtained during the experiment.

What does the percentage yield do and how is it calculated?

• Compares the actual yield and the theoretical yield

• Percentage yield = (actual yield divided by theoretical yield) x 100

Why is yield less than expected?

• Not all of reactants are used up - reaction may be incomplete

• Some product is lost

• May be unwanted side reactions taking place

What is atom economy and how is it calculated

• A method of showing how efficiently a reaction makes use of the atoms in the reactants.

• Atom economy = (relative formula mass of the useful product divided by sum of relative formula masses of reactants) x 100

What is a by-product?

A product which is also formed alongside the desired product

What is a reversible reaction?

Reactions in which the products can react to form the reactants as well as the reactants forming the product

When has dynamic equilibrium been reached?

When the rate of the forward reaction is equal to that of the back reaction

What are the graphs of equilibrium?

What do characteristics of equilibrium state?

• Concentrations are constant

• Forward rate = backwards rate

• Must be a closed system

• All species of equation must be present in mixture

• Can be obtained from reactants/products

What does Le Chatelier's principle state?

If a system of equilibrium is subjected to change, the position of equilibrium will shift in order to minimize the effect of the change.

What does exothermic mean?

• Leave heat

• Heat is produced causing temperature to increase (HOT)

• ΔH = -

• E.g.combustion

What does endothermic mean?

• Goes in heat

• Heat is taken in causing temperature to decrease (COLD)

• ΔH = +

• E.g photosynthesis

Which direction does equilibrium shift to if temperature increases?

Endothermic

Which direction does equilibrium shift to if temperature decreases?

Exothermic

Which direction does equilibrium shift to if gas pressure increases?

Direction forming fewer gas molecules

Which direction does equilibrium shift to if gas pressure decreases?

Direction forming more gas molecules

Which direction does equilibrium shift to if concentration increases?

Direction using up added substance

Which direction does equilibrium shift to if concentration decreases?

Direction making more of the removed substance

What are the optimum conditions?

• Fe catalyst

• 200 atm pressure

• 450°C temperature

What are key ingredients of fertilizers?

• Nitrogen N

• Phosphorus P

• Potassium K

What are fertilizers used for?

• Growth

• Repair

• Plants need to make amino acids and make proteins and new DNA for new cells

What is ammonium nitrate made from and what is the symbol equation?

• Ammonia and nitric acid

• NH₃ + HNO₃ → NH₄NO₃

What are advantages and disadvantages of batch?

Advantages

• Can meet individual orders

• Less damaging if contaminated

• Easy to stop production

Disadvantages

• Labour intensive

• Energy to heat up each time

What are advantages and disadvantages of continuous?

Advantages

• Known rate of production

• Not labour intensive

• Don't heat up energy each time

Disadvantages

• More damaging if contaminated

• Hard to stop production

What is NH₃?

Ammonia

What is NH₄⁺?

Ammonium

What is the equation for ammonia?

N₂₍₉₎ + 3H₂₍₉₎ ←→ 2NH₃₍₉₎

What is the symbol equation for ammonium sulphate?

NH₃ + H₂SO₄ ←→ (NH₄)₂SO₄

What is molar gas volume?

1 mole of a gas at room temperature (25°C) and pressure (100KPa) occupies 24 dm³ or 24000cm³