What are properties of a primary standard solution?
- can be obtained in pure form - (high percentage purity)
- will not absorb moisture from air (non-hygroscopic) and will not react with air particles
- relatively high molar mass
- stable
Why is NaOH not a primary standard solution?
- absorbs moisture from air (hygroscopic) and reacts with air particles
- low percentage purity
- Relatively low molar mass
Is Na2CO3 a p or non p standard chemical
- can be obtained in pure form - (high percentage purity)
- will not absorb moisture from air (non-hygroscopic) and will not react with air particles
- relatively high molar mass
- stable
Equipment of Titration
Volumetric flask
conical flask
buret
pippete
indicator
retort stand
white tile
funell
distilled water
What are the main points of a titration graph
End point
Equivalence point
what is end point
point which indicator chnages colour permanantly
what is equivalence point
point at whcih equal moles of H+ and OH- ions are mixed
What to use when washing
detergent and warm water
Why doesnt water dilute the sodium carbonate solution in conical flask when rinsing with distilled water when delivering hcl from buret
As we only care about the moles of sodium carbonate
- Adding distilled water does not affect the titre because it only dilutes the solution without changing the number of moles of sodium carbonate present, so the same amount of hydrochloric acid is still required to reach the endpoint.
What do you rinse pipette with
rinse with distilled water initially then final rinse is the solution transferring
what do you rinse conical flask
rinse with distilled water only
what do you rinse burette with
pre rinse with distilled water then final rinse is with solution being filled with
what is volumetric flask rinsed with
distilled water only
what is the beaker rinsed with - to store primary standard
rinse with the solution storing
what is aliquot meaning
solution transferring by pipette
What happens if Burette is not rinsed with solution being put in it (HCL)
- water inside will dilute the hcl
- concentration of hcl will be less than actual
- volume of titre is more than actual
hence moles of hcl is over than actual - the result is that moles of naoh mass and percentage will be overestimated.
What happens if pipette is not rinsed with solution being transferred (naoh)
- water inside will dilute the naoh solution
- concentration of hcl will be less than actual
- moles of naoh is less than actual which is being delievered to conical flask
-volume of titre is less than actual - the result is that moles of naoh mass and percentage will be underestimated.
What happens when rinse conical flask with distilled water
no effect as the reaction between acid and base depends on mole ratio not conc.
Explain what is meant by a secondary standard
A secondary standard is made when the substance cannot be used as a primary standard.
give an example of how a secondary standard is produced
for e.g HCl cannot be used as a primary standard as it is not available as a solid. To prepare a standard of HCl, we would need to make a solution of HCl with an approximate concentration, e.g about 0.1 mol L^-1, and do a titration against a primary standard such as sodium carbonate. This would allow us to accurately calculate the concentration of HCl, and it could then be used as a standard solution in titrations.
