Aos Flashcards
Why is sodium ions smaller then fluorine ions
They have both lost and gained an electron so their electronic config will be the same. Sodium has more protons and so therefore has a bigger nuclear charge so it has a stronger attraction and will
Attract the electrons closer making it smaller
The student used a wash bottle containing deionised water when approaching the end point to rinse the inside of the conical flask- explain why this improved the accuracy of the titration
Ensures that the acid wasnt left behind to react and give invalid results- (and so all of the reactants are in the mixture at the bottom)
Give the meaning of the term concordant titres
They are within 0.1cm cubed of each other
If it wants the total moles of gas but there are two gas products with a 4 and a 1 co efficient in front of them what do you do
There is 5 moles of gas in total so use that in the mole ratio
How to get from m cubed to cm cubed
Times million
The maas of mgo obtained in this exp in slightly less than expected from the mass of mg no3 used suggest one practical reason why
As some of the solid may have been lost for example blown away with the gas
How do you work out the percentage uncertainty
Use the value they gave you eg uncertainity of 0.15 and divide that by your value
Suggest a reason other than apparatus innacuracy for why the mr is smaller when experiemental
As the volume of gas may be greater than the true value as some air may have leaked into the syringe and therefore the mass would increase decreasing the volume or - temp changed increases mass inc mr decreases
Suggest a safety precaution needed for toxic gases
Carry out the exp in a fume cupboard to avoid toxic vapour
The student rinsed the burette before filling it with sodium hydroxide. Explain why the student should use the sodium hydroxide solution rather than water
As water would dilute the sodium hydroxide
If asked to work out the ideal gas pressure but given the total volume of both gases what do you do say the vol is 5000cm cubed
Convert 5000 to dm divide by. A million 5.00 times 10-3 then put everything into the pV nRT equation and re arrange it to work out the moles and then once you have your moles the total right side moles (big numbers in front of the gases added up to 5) so divide the moles by 5 to get one mole. That is the same as the left side so then the moles of b202 is that number. Then work out its rfm and times it and bang theres your mass
In the reaction BCl3(g)+1 1/2 H2(g)——>B(s)+ 3HCl(g) apart from changing the reaction conditions suggest one way a company producing pure boron could increase its profits from this reaction
By selling the hcl
For a question where it wants you to work out empirical formula of smth and it gives you mass f smth before heating and after what would u use
After bc obvs u need it when its dry not when water is in it
sodium hydroxide is often sold as a concentrated solution containing 12.0moldm-3 of sodium hydroxide. calculate the volume of water that should be added to 10cm cubed of a 12.0moldm-3 solution of sodium hydroxide to make a 0.250 moldm-3 solution
10 times 12 divided by 0.25= 480 cm cubed
sodium nitrite formula and mr
nano2 and 69
