Oxidising and reducing Flashcards
What do displacement reactions normally involve?
a metal high in the ECS reacting with the ions of a metal lower in the ECS
What is OILRIG?
Oxidation Is Loss Reduction Is Gain
What are the only metals that react with acids?
metals above hydrogen in the ECS
What is a reducing agent?
a substance which donates electrons. In donating electrons, a reducing agent causes the reduction of another element, and in the process, is oxidised.
What is an oxidising agent?
a substance which accepts electrons. An oxidising agent causes the oxidation of another reactant, and in the process is reduced
Where are the best reducing agents found and why?
substances which easily give away/ donates electrons, e.g. group 1. They have low electronegativity. These substances are found at the top of the ECS, e.g. lithium and caesium
Where are the best oxidising agents found and why?
who easily accept electrons e.g. group 7. They have high electronegativity values. These substances are found at the bottom of the ecs e.g. fluorine and chlorine.
Apart from elements what does the ECS also contain?
compounds, group ions and molecules which can all act as oxidising or reducing agents
Give an example of a strong oxidising agent that is a compound?
permanganate ion which is reduced and converted to manganese ions
Give an example of a molecule which is an oxidising agent?
Hydrogen peroxide
Give an example of a molecule which is a reducing agent?
carbon monoxide
What are the 5. rules for writing out complex ion-electron equations?
- Write out equations with ions named in question and balance non-oxygen element
- Balance oxygen by adding water to opposite side
- Balance hydrogen by adding hydrogen ions to opposite side
- Calculate charge on each side
- Balance charges by adding electrons to side containing hydrogen ions.
What are oxidising agents used as? (3)
biocides, disinfectants and bleaches
What are biocides used for?
killing fungi and bacteria, and inactivating viruses
Give a common strong oxidising agent used in disinfectants?
sodium chlorate
What can bleaches be used with? give an example of a common oxidising agent?
textiles, paper and hair. hydrogen peroxide is commonly used is hair bleach. The oxidation process can change the structure of coloured compounds and cause them to become colourless
What are redox titrations based on?
redox reactions
What is a standard solution?
solution of an accurately known
How would you prepare a standard solution(use vitamin C)|?
a vitamin C tablet was dissolved in 50cm3 of water in a small beaker.
The solution was then transferred to a 250cm3 standard flask
The beaker was washed out with water and the rinsings were then transferred to the standard flask
Very carefully, water was finally added to the graduation mark (250cm3 line) on the standard flask with a dropping pipette. The flask was then stoppered and inverted several times.
How would you carry out a titration(use vitamin C)|?
25cm3 of the vitamin C solution was taken and pipetted into a conical flask.
A few drops of starch indicator was added to the conical flask.
The iodine solution was prepared with a concentration of 0.025 mol l-1 and added from the burette to the conical flask.
when the solution turned blue/black the volume of the burette was noted
The experiment was repeated until concordant results were obtained
What is chromatography?
a method of separation of mixtures
What are the 2 different types chromatography ?
paper chromatography
Gas-liquid chromatography
What does paper chromatography measure?
the distance moved by the separated substance in relation to the distance moved by the solvent
What does separation usually depend on?
the size of the molecules (larger molecules take longer to separate)
the polarity of molecules
What is gas chromatography?
uses an unreactive gas, e.g. helium. A liquid sample mixture is injected into the column and vaporised before the gas (helium) takes it through the column.
Why is gas chromatography useful?
it can separate out complicated mixtures of chemicals using only a small sample of material
What is the name given to the chart recorder in which a computer presents the results from gas chromatography?
chromatogram
What is the retention time?
the time it takes for a peak to appear
Describe the retention time for small and large molecules?
small molecules vaporise quickly and appear first.
Larger molecules take longer to pass through the chromatography instrument
What does the area under the graph indicate?
how much of a substance is present
What are the 4 uses of chromatography?
testing blood alcohol levels
food industry (to analyse components of a substance or detect contaminants)
medicine (to determine the components of a potential drug)
environmental (to monitor the components of water supply)
