Volumetric analysis
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in an experiment why would no stopper be used
to allow gas to escape
Why should deionised or distilled water be used rather than tap water
impurities may be present in tap water
Describe how a burette should be prepares and set up ready to begin a titration
rinse the burette with the required solution fill burette above the scale with the solution filter funnel used should be removed reading should be taken from the bottom of the meniscus
suggests why the activation energy for a reaction may be low
the reaction is spontaneous
Suggests points of good practice that a student should follow to ensure an accurate end point is achieved in a titration
all readings taken at eye level All glassware is clean and has been rinsed with the solution to be used. White paper under the flask to easily identify the end-point.
Describe how a test using fehlings or benedicts solution should be carried out
Sample and Benedict’s solution in a test tube in a hot water bath
Describe how to set up an enthalpy of combustion reaction
measure temperature of water at the start weight the fuel at the start burn the fuel then extinguish the flame measure the maximum temperature weight the fuel at the end
How to make up a standard solution
weigh mass of solute dissolve in small volume of deionised water in a beaker transfer to standard flask with repeat rinsings fill flask with deionised water until the bottom of the meniscus is line marked stopper and invert to mix
What is the most accurate piece of equipment to measure volume
pipette
Why would gas be collected over water
insoluble gases where a dry sample is not required
Why would gas be collected using a gas syringe
soluble gases where a dry sample is required
What is a titration used for
accurately determine the volume of solution required to reach the end point of a chemical reaction
suggest a disadvantage of using a methanol fuel cell when compared to a hydrogen fuel cell
the use of methanol as a fuel would produce carbon dioxide
Give reasons why a process is profitable
low cost of reactants exothermic reaction so the energy released could be used in other processes costs are less as low pressure is used
Explain why the relative rate of a reaction decreases as the concentration of the solution decreases
fewer collisions are taking place as concentration decreases
What piece of glassware is used to prepare a standard solution
volumetric flask
Describe how a 250cm of a standard solution would be prepared
dissolve in small volume of deionised water transfer with rinsing up to the line in a standard flask
What is filtration
used to separate a solid reside from a liquid or a solution
In an experiment to measure the rate of reaction, which piece of equipment is used to collect gas evolved?
gas syringe
State the measurements required to calculate the mass of an alcohol burned in an enthalpy of combustion reaction
mass of burner before and mass of burner after
What is the end point of a titration
the point where the reaction has just reached completion
Describe fully a method to accurately measure the mass of a 10.0 cm solution
Use a 10cm3 pipette to transfer the solution to a beaker that has been tared on a balance
how can a gas that is insoluble in water be collected
displacement of water
To ‘transfer quantitatively’ means that all of the iron tablet solution must be transferred into the volumetric flask. Describe how this is carried out in practice.
Rinse beaker and transfer the rinsing’s to the flask