Jotter 2 Flashcards
What is Oxidation?
It is a loss of electrons in reactants in any reaction.
What is Reduction?
It is a gain of electrons in reactants in any reaction.
When in a Redox reaction does Oxidation and Reduction occur?
At the same time.
How do you identify Oxidation and Reduction in a Redox reaction?
Using ion-electron equations.
Where in the data booklet do you find elements and compounds that are strong reducing agents?
Elements and compounds in the top right of the electrochemical series.
Where in the data booklet do you find elements and compounds that are strong oxidising agents?
Elements and compounds in the bottom left of the electrochemical series.
What is an indicator of reduction or oxidation in an element?
It’s electronegativity.
What is the pattern of electronegativity of a reducing agent?
Elements with low electronegativity tend to form ions by losing electrons and are therefore act like reducing agents.
What is the pattern of electronegativity of a oxidising agent?
Elements with high electronegativity tend to form ions by gaining electrons and are therefore act like oxidising agents.
Where in the periodic table are reducing and oxidising agents?
Strongest reducing agents are found in group 1 and the strongest oxidising agents are found in group 7.
What else except elements can be used for oxidation or reduction?
Compounds, group ions and molecules.
What is the gas that used in a blast furnace to reduce iron (III) ions to iron atoms?
Carbon Monoxide.
What are some useful oxidising agents.
Hydrogen Peroxide and Potassium Permanganate.
Potassium Permanganate is a useful oxidising agent, what is its use?
It is very effective against fungal infections such as athletes foot and is also used to prevent disease in fish in ponds.
Hydrogen Peroxide is a useful oxidising agent, what is its use?
Hydrogen Peroxide breaks down coloured compounds meaning it can be used as bleach for clothes and hair.
Where can examples of complex ion-electron equations be found?
In the data booklet and they usually contain hydrogen ions and water.
In what conditions will most of the Redox reactions occur?
In neutral or acidic conditions.
What is one of the things you should make sure happens when balancing a redox equation?
You need to make sure that the same number of atoms is each element is being oxidised or reduced on each side of the half equation.
What should you do in a redox equation if oxygen atoms are present?
Balance them by adding water molecules to the opposite side of the half equation.
What should you do in a redox equation if hydrogen atoms are present?
Balance them by adding hydrogen ions on the other side of the half equation.
What should you make sure both half reactions are in terms of charge?
You have to make sure they have the same overall charge on each side which is achieved by adding electrons.
Why must reactions be controlled in industrial processes?
They must be closely controlled as if the rate is too slow then the reaction will not be economically viable but if it’s too high then an explosion might occur.
What must particles do to have a successful chemical reaction?
They must collide with each other.
When particles collide what are the 2 important factors that must happen?
There must be enough kinetic energy at which these particles collide in order for the reaction to occur (activation energy).
The particles must collide with the correct collision geometry (angle).
In collision theory what does the letter E represent?
The minimum kinetic energy for a reaction to occur.
What happens when the reactant particles collide with the required activation energy (Ea)?
They form an activated complex which is an unstable arrangement of atoms which breaks down to form the products of the reaction.
What happens if particles collide with the correct activation energy but the wrong collision geometry?
The activated complex will not be formed meaning no reaction will occur.
What effect will reducing the particle size have on the rate of reaction in collision theory?
Reducing the particle size will increase the surface area of the reactant as this means that more particles are exposed resulting in a higher chance for successful collision.
What effect will increasing the concentration of the reactants have on the rate of reaction in collision theory?
An increase in concentration of the reactant will overall result in more particle allowing for a higher chance of collision, meaning the rate of reaction is increased.
What effect will increasing the temperature have on the rate of reaction in collision theory?
Raising the temperature will allow the activation energy to be reached o even surpassed and will speed up the rate of reaction as particle will be moving quicker.
What does increasing the temperature increase other than rate of reaction?
Raising the temperature increases the kinetic energy meaning more particles can collide successfully as they will have the right activation energy.
What effect will increasing the pressure have on the rate of reaction in collision theory?
More pressure will result in the particles of the reactant being packed closer together meaning more collisions can occur as there is now a smaller space but the same amount of particles.
What effect will a catalyst have on the rate of reaction in collision theory?
A catalyst will provide the reaction with a different reaction pathway with a lower activation energy meaning more particles will be able to successfully collide.
What needs to be done in order to record the average rate of reaction?
Record the change in mass of the reactants or products in a given time.
OR
Record the change in volume of the reactants or products in a given time.
ESSENTIAL
Change in the concentration of reactants or products.
What else can be done when it is too difficult to measure the change in a chemical reaction (for example colour change)?
The relative rate calculation can be used instead which is a reaction which consists of:
1 over the time taken for the reaction.
AND
1 over the rate over reaction.
What is enthalpy change?
It is the difference between the energy of the reactants and the energy of the products and is represented by a (delta) H
What is the enthalpy change in an exothermic reaction?
Always negative.
What type of chemical reactions are most reactions part of?
Exothermic (meaning they release energy).
What might exothermic reactions in industry require in order to be removed to prevent the temperature from rising to a dangerous level?
Heat.
What 3 groups are alcohols classified in?
Primary, Secondary and Tertiary
Where can the boiling points and melting points of alcohols be found?
In the data booklet (page 10)
What causes the boiling point to increase in alcohols?
An increase in the number of carbon atoms per molecule.
Why do more hydroxyl groups increase the boiling point of alcohols?
Since hydroxyl groups (-OH) are polar this leads to more hydrogen bonding meaning more energy is required to break them.
What is volatility?
Volatility is the ease of evaporation.
Why does volatility decrease?
Volatility decreases as the number of carbon atoms per molecule increases.
What is the process for the preparation of of ethanol called?
Fermentation.
What is used in the preparation of ethanol?
Glucose (C₆H₁₂O₆) and the enzyme Zymase that is found in yeast, this process converts glucose into ethanol and carbon dioxide.
How strong of a solution can fermentation produce?
Fermentation can only produce a solution with a concentration of 15% as anything higher kills the yeast.
What process is required to increase the concentration of an alcohol from 15% to the 40% of a spirit?
Distillation
What is Synthesis Gas (used in industrial preparation of methanol)?
It is a mixture of carbon monoxide and hydrogen.
How is synthesis gas made?
It is made by steam reforming either coal or methane over a nickel catalyst.
What needs to be combined with Synthesis Gas to form Methanol?
Zinc Oxide Catalyst.
What can methanol be converted into and why is it important?
Methanol can be converted into Methanal which is used to make thermosetting plastics.
What is Dehydration?
It is a process which involves the removal of water from a compound.
What product does the Dehydration of alcohol give you?
An Alkene.
What is lost within an alcohol during dehydration?
The hydroxyl group from one carbon and one hydrogen from an adjacent carbon (this forms an alkene).
What else other than Aluminium Oxide can be used as a catalyst during the dehydration of an alcohol?
Concentrated Sulphuric Acid as it is a strong dehydrating agent.
What might happen to larger secondary or tertiary alcohols when they are dehydrated?
They can form a mixture of isomers.
What do alcohols produce when undergoing combustion?
Carbon dioxide and water.
What is Oxidation?
It is when the oxygen to hydrogen ratio increases and is accomplished by removing a H from the Hydroxyl group.
What is complete oxidation also known as?
Combustion.
How many times can a primary alcohol be oxidised and what are the products?
2 times with the first creating Aldehydes and the second creating Carboxylic Acids.
How many times can a secondary alcohol be oxidised and what are the products?
1 time with that one time creating Ketones.
How many times can a tertiary alcohol be oxidised and what are the products?
Tertiary alcohols can’t be oxidised.
What substances help oxidation reactions take place?
Oxidising Agents.
What are 2 Oxidising Agents that are most commonly used with alcohols?
(Hot) Copper (iii) Oxide and Acidified Potassium Dichromate.
What happens when alcohol is oxidised with Acidified Potassium Dichromate?
The dichromate ion is reduced to the Cr³+ ion.
What happens to (hot) Copper Oxide when it is used in the oxidation with alcohol?
The Copper Oxide is reduced to Copper Metal and the alcohol is oxidised.
When primary alcohols are oxidised what is lost in the first stage of oxidation?
Hydrogen
What happens when oxidation is applied to carbon compounds?
Results in an increase in the oxygen to hydrogen ration.
How many hydrogens are removed when a primary or a secondary alcohol is oxidised?
2, 1 from the hydroxyl group and one from the adjacent carbon.
Why can’t a tertiary alcohol be oxidised?
It doesn’t have any hydrogens on the adjacent carbon atom.
When primary alcohols are oxidised what is gained in the second stage of oxidation?
Oxygen is gained
What does reduction result in when used in carbon compounds?
Results in the decrease in the oxygen to hydrogen ratio.
What is the functional group in an aldehyde?
Carbonyl Group.
What do aldehyde names end in?
-al.
What is another name for an aldehyde?
Alkanal.
What functional group do ketones contain?
Carbonyl Group.
What is the difference between the structure of ketone and aldehyde?
For aldehydes the functional group is on the outside meanwhile the functional group on a ketone is in the middle.
What is the general formula of Aldehydes?
CnH₂nO
What is the general formula of Ketones?
CnH₂nO
What do Carboxylic Acid’s end in when named?
-anoic.
What functional group do Carboxylic Acid’s contain?
Carboxyl Group (-COOH)
Just like other acids what can Carboxylic Acid react with?
Bases (e.g Water, Salt)
What can be done to Carboxylic Acids in order to revert them back to an aldehyde?
The acid can be reduced in stages back to its parent aldehyde.
What are isomers?
They are compounds that have the same structural formula but a different general structure.
What can aldehydes be oxidised by to create a Carboxylic Acid?
Benedict’s (Fehling’) Solution, Tollen’s Reagant and Acidified Potassium Dichromate.
When Aldehydes are oxidised into Carboxylic Acids what colour changes are experienced depending on the Oxidising Agent?
Benedict’s Solution- from blue to orange-red
Tollen’s Reagant- from clear to silver
Acidified Potassium Dichromate- from orange to green
What do Ketones not react with?
Mild oxidising agents
How are Esters made?
They are formed by reacting an alcohol with a Carboxylic Acid through the reversible process of Condensation.
What is the functional group of an ester?
Ester Link
O
||
C — O
What is Esterification?
It is a condensation reaction that occurs in esters.
What is a condensation reaction?
It is when small gas molecules join together to form bigger liquid molecules by the elimination of water.
What do the ends of an alcohol end in when naming the alcohol?
-ol
How does esterification occur?
It happens when a mixture of an alcohol, Carboxylic acid and concentrated sulphuric acid (acting as a catalyst and absorbing the water) are heated up.
Is Esterification reversible?
Yes
Where is the remaining mixture poured after Esterification?
Into a Hydrogen Carbonate Solution in order to neutralise the sulphuric acid and any Carboxylic acid that may be left.
What happens in the hydrolysis of esters?
Large molecules are broken down into smaller molecules by water.
What do esters produce when they are hydrolysed?
They can produce their parent Carboxylic acid and their parent alcohol.
What is the opposite of a condensation reaction?
Hydrolysis.
What makes esters have a reversible reaction?
The fact that condensation is used to create an ester meaning water is removed during the process but hydrolysis is the addition of water which breaks it down into its parent alcohol and it’s parent Carboxylic acid.
What are some of the uses of esters?
Flavouring, fragrances and solvents.
Why are fats more useful than carbohydrates?
They provide more energy per gram.
Are fat molecules soluble?
No, meaning they form large droplets.
Why is fat essential for the body?
It transports and store fat soluble (non-polar) vitamins such as K, A, D and E.
Why are animal fats important for us?
They contain important fat soluble vitamins.
What origins do natural oils have?
Vegetable and marine.
What origins do natural fats have?
Animal.
What is the difference between oil and fat?
Oils have a higher level of unsaturation and contain much more C=C double bonds than fats.
What does unsaturated mean?
A molecule that contains carbon-carbon double bonds or carbon-carbon triple bonds.
What do solid fats tend to be?
Saturated.
What do liquid oils tend to be?
Unsaturated.
What are fats and oils based on?
Glycerol and propene-1,2,3-triol.
What are natural fats and oils a mixture of?
Triglyceride compounds.
What are the components that make up a natural fat or oil joined by?
Condensation reactions.
Where are any double bonds found in natural oils or fats?
In the acid chains.
How are fats and oils formed?
They are formed by a combination of 3 moles of fatty acids to 1 mole of glycerol-triglyceride. Meaning there are 3 ester linkages in the one molecule.
What happens to a fat or an oil when it is oxidised?
It goes rancid.
How do you work out if a fatty acid is saturated or unsaturated?
Count the number of carbon and hydrogen atoms as saturated fatty acids have double the amount of hydrogen atoms as carbon atoms.
Why do fats have higher melting points than oils?
Fat molecules aren’t as distorted meaning they can pack closely together which increases their melting point.
Why do oils have a lower melting point than fats?
The lower melting point is related to the higher degree of unsaturation because the presence of C=C in oils distorts the long fatty acid chains and the shape of the molecule meaning they can’t pack together.
What do unsaturated oils have less of in terms of intermolecular forces?
London dispersion forces meaning their melting and boiling points are low.
What do fats and oils have in common to esters in terms of their reaction?
They are both reversible.
By what process can oils be converted into fats?
Hydrogenation, and must be done over a nickel catalyst (in industry known as ‘hardening of oils’)
What is Hydrogenation?
It is the addition of a hydrogen molecule across the C=C.
What is now done to oil due to health concerns?
The oil is blended with butter. Creating margarine which increases the melting point of oil.
What are soaps?
They are sodium or potassium salts of fatty acids.
How are soaps made?
They are made by the hydrolysis of fats/oils by metal hydroxide.
What is formed in soap with the presence of an alkali?
A water soluble ionic salt of Carboxylic acid.
How is fat hydrolysed?
By heating.
What are detergents?
They perform the same function as soap but are synthetic products that are made from crude oil as opposed to soap being made from natural fats.
What are the advantages of detergent over soap?
They have better cleaning power, they are easier to rinse away and they do not form ‘scum’ in hard water unlike soaps.
What is hard water?
It is water that contains high levels of dissolved metal ions.
What is the structure of soap?
It is a long covalent hydrocarbon chain that contains a hydrophobic tail (non-polar and oil soluble) and hydrophilic head (polar attracted to water).
What are the structures called that are created when soap is used?
Micelles.
What does an emulsion contain?
It contains small droplets of one liquid dispersed in another liquid.
What are emulsions in food?
They are mixtures of oil and water.
What is the function of an emulsifier?
To prevent a polar and a non-polar from separating.
How are emulsifiers that are used in food made?
They are made by reacting edible oils with glycerol in order to form molecules in which only 1 or 2 fatty acid groups are linked to the glycerol backbone.
What is the difference between the structure of an oil and the structure of an emulsifier?
An emulsifier is simply a fat or an oil that has 1 or 2 fatty acids missing.
What are emulsifiers classed as?
Either monoglycerides or diglycerides.
How the presence of an emulsifier usually made clear on packaging?
By E- numbers with the most common being E-471
What foods are emulsifiers added to?
Sauces, bread, biscuits, ice cream and low fat spreads.
What can proteins be classified as?
Fibrous.
What are proteins in terms of structure?
5 times longer than they are wide.
What types of proteins are there and what are their uses?
Keratin- nails and hair
Collagen- tendons, bone and muscle
What is an element that is essential in proteins?
Nitrogen.
What is a globular protein?
They are spiral chains that are twisted into compact units that have a very specific shape allowing them to have hydrogen bonding with other substances.
What are examples of amino acids?
Glycine, Alanine and Tyrosine
What are amino acids that can only be taken in through food called?
Essential amino acids.
By what process do we digest proteins?
Hydrolysis.
What can amino acids act as?
Acids and bases as they contain a group and an amine group, which is a base.
How is an amide link formed?
It is formed by the reaction of an amino acid group with a carboxyl group.
What are proteins in terms of structure?
Condensation Polymers.
