Volumetric analysis Flashcards
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
What is an indicator
a substance which changes
colour when a reaction is just complete
What is the correct way to measuring the mass of a solid
weighing by difference
Describe a procedure to accurately weigh out a 50·0 g sample of iodised
table salt.
Set the balance to zero, place weighing bottle on balance. Record empty mass. Add 50.0g of salt to weighing bottle on balance and record the new mass. The difference in masses is the mass of the substance in the bottle.
What is the burette used for in a titration
gradually and accurately add small volumes of solution to the conical flask
Suggest ways to maximise profit in an industrial process
recycle gases
use a catalyst
using the by products
Explain why the aluminium foil needs to be heated at the start of
the preparation, despite the reaction being highly exothermic.
To provide the activation energy
What is a condensation reaction
two small molecules join together to form a larger molecule with the loss of water
Why would tap water not be used when making a standard solution
it contains metal ions that could alter the concentration
What does transfer quantitively mean
transfer with repeat rinsings
Describe how to form a solution
use pipette to measure volume required and transfer directly into standard flask
fill flask with deionised water until bottom of the meniscus is on the marked line
stopper and invert to mix
Suggest why fuel cells are thought to be more environmentally friendly than aviation fuels
water is the only product
Name factors that are important influences on the design of an industrial process
opportunities for recycling
marketability of by products
product yield
Give a reason for titrating several smaller samples of fruit drinks
improve reliability
What are the environmental consideration in an industrial process
minimising waste
avoiding the use of toxic substances
designing products which will biodegrade if appropriate
Explain the steps to collect, dry and weigh a precipitate
weigh the filter paper
filter the precipitate
wash the precipitate with water to remove any impurities
dry the precipitate in the oven
weigh the precipitate and the filter paper
