C5 - Monitoring and controlling chemical reactions

What is theoretical yield?

the maximum amount of product that can be produced from a given amount of reactant

What is a limiting reagent?

The reactant that is fully consumed in a reaction

What is percentage yield?

actual yield/theoretical yield x 100

Why is actual yield always less than theoretical yield?

reactants react in a diffeent way than expected / reaction may to not go to completion (not all reactants reacted) / you may lose some product when you separate and purify it

What is atom economy?

the amount of starting materials that end up as desired products

How do we calculate atom economy?

Mr of desired products / total Mr x 100

What does high atom economy mean?

Less waste products

What do you need to consider when choosing a reaction pathway?

percentage yield / atom economy / by-products / rate of reaction / equilibruin position

What must you consider about by-products?

toxicity (if they are toxic they are expensive and hazardous to get rid of)

What is a solute?

substance that is dissolved

What is a solvent?

substance in which the solute dissolves

What is a solution?

a mixture of solute and solvent

How do convert cm³ to dm³?

1 dm³ = 1000 cm³

What is concentration?

the amount of solute in a solvent

What is concentration measured in?

mol/dm³, g/dm³

What is the equation liking moles, concentration and volume?

concenctration = moles / volume

What type of reaction does a titration follow?

neutralisation

Why do titrations use a single indicator?

this shows a single change in colour near the end point

Name a single indicator.

phenolphthalein / methyl orange / litmus

What colour is phenolphthalein in the prescence of an acid?

colourless

What colour is phenolphthalein in the prescence of an alkali?

pink

What colour is phenolphthalein in a neutral solution?

colourless

What colour is methyl orange in the prescence of an acid?

red

What colour is methyl orange in the prescence of an alkali?

yellow

What colour is methyl orange in a neutral solution?

yellow

What colour is red litmus paper in the prescence of an acid?

red

What colour is red litmus paper in the prescence of an alkali?

blue

What colour is red litmus paper in a neutral solution?

red

What colour is blue litmus paper in the prescence of an alkali?

blue

What colour is blue litmus paper in the prescence of an acid?

red

What colour is blue litmus paper in a neutral solution?

blue

What is meant by the 'end point'?

the point at which the indicator changes colour

What volume does 1 mol of a gas measure at RTP?

24 dm³

What is the mol calculation for gases?

moles = volume/24

What is activation energy?

energy needed to start a reaction

What methods can we use to determine rate of reaction?

gas syringe / upturned measuring cylinder / disappearing cross

How can we increase rate of reaction?

increase pressure / increase concentration / increase surface area / use catalyst

How does increasing the temperature increase the rate of reaction?

more kinetic energy

How does increasing the surface area increase the rate of reaction?

reactions happen on the surface, so there is more particles to react with

How does increasing the pressure increase rate of reaction?

more particles in a given volume

How do catalysts increase the rate of reaction?

lowering the activation energy

What is a reversible reaction?

a reaction where the products can react together to form the original reactants

What is dynamic equilibrium?

when the rate of forwards and backwards reaction in a mixture are equal

What are the conditions of dynamic equilibrium?

rate of forward reaction = rate of backwards reaction / closed system / unchanging amounts at equilibrium

What happens to the equilibrium position when you increase pressure?

the equilibrium goes to the side with the fewest moles of gas

What happens to equilibruim position when you increase temperature?

moves in endothermic direction