Core practicals

Question 1

How can you work out the volume of gas produced

Answer 1

measure out volume of HCl
add sodium carbonate
connect the gas syringe delivery tube
allow to go till completion
record volume of co2 formed
repeat with different masses of sodium carbonate

Question 2

assumptions made from volume of gas practical

Answer 2

amount of gas lost between adding Na2Co3 and connect tube is negligible

delivery tube is airtight

goes till completion

Question 3

should you hydrolysis halogenoalkane with hydroxide or water

Answer 3

OH- better nucleophile as full formal negative charge whereas in water oxygen carry partial negative charge so nucleophilic substitution will be slower.

Question 4

how can you measure rate of hydrolysis

Answer 4

add silver nitrate
set up three test tubes at 50C with ethanol and silver nitrate
add chloro bromo and iodoalkane
stop watch see which precipitates first
chloro - white bromo - cream iodo - yellow
yellow form first as C-I has low bond enthalpy so easiest to break

Question 5

how to make standard solution

Answer 5

1. Weigh the sample bottle containing the solid on a (2 dp) balance.
2. Transfer solid to beaker and reweigh sample bottle.
3. Record the difference in mass.
4. Add distilled water and stir with a glass rod until all the solid has dissolved.
5. Transfer to a volumetric flask with washings.
6. Make up to the 250cm$ mark with distilled water.
7. Shake flask.

Question 6

uncertainty of burette

Answer 6

0.05+-

Question 7

steps for titration

Answer 7

measure know volume of solution in volumetric flash and in the other put other solution

add indicator tap of burette opened till indicator change colour

multiple runs for concordant results within 0.1cm3

Question 8

why is uncertainty doubled in titrations

Answer 8

because two burette readings made to obtain titre

Question 9

methyl orange

Answer 9

red in acid
yellow in alkali

Question 10

phenolphthalein

Answer 10

colourless in acid
pink in alkali