Quick question (1 Viewer)

[Haku]

for the hsc paper 2002, for the MC question 8, why is the conical flask i the titration need to be rinsed with water?

well the successone book say the answer is A. but base is going to be transfered from the pipette to the conical flask, so both the pipette and the conical flask should be washed with base right?

and for the same paper, Q19, the successone book says the a nucleus is unstable when the atomic mass is greater than 83... is that right?

i clearly remember that its unstable when it have an atomic number 92 or greater. for low mass nucleus the neutron to proton ratio should be around 1:1 and for higher mass ones but not going over atomic number 92 can be around 1.5:1
example given is carbon-14

 

[serge]

for the hsc paper 2002, for the MC question 8, why is the conical flask i the titration need to be rinsed with water?

well the successone book say the answer is A. but base is going to be transfered from the pipette to the conical flask, so both the pipette and the conical flask should be washed with base right?

and for the same paper, Q19, the successone book says the a nucleus is unstable when the atomic mass is greater than 83... is that right?

i clearly remember that its unstable when it have an atomic number 92 or greater. for low mass nucleus the neutron to proton ratio should be around 1:1 and for higher mass ones but not going over atomic number 92 can be around 1.5:1
example given is carbon-14

I forget the real reason for the conical flask part
(I dont think i ever really questioned why the
conical flasks was rinsed with water, but
i know for sure that, that's the correct way)

the chemistry definition for unstable
has every element past 82
being radioactive / unstable
(your neutron to proton ratio is
correct)

1:1 for elements under 20
1.3:1 for greater than 20
1.5:1 for near the 80s

in physics they mention every
transuranic element is radioactive/
or unstable, (meaning every element
greater than 92)

 

[Dreamerish*~]

for the hsc paper 2002, for the MC question 8, why is the conical flask i the titration need to be rinsed with water?

well the successone book say the answer is A. but base is going to be transfered from the pipette to the conical flask, so both the pipette and the conical flask should be washed with base right?

and for the same paper, Q19, the successone book says the a nucleus is unstable when the atomic mass is greater than 83... is that right?

i clearly remember that its unstable when it have an atomic number 92 or greater. for low mass nucleus the neutron to proton ratio should be around 1:1 and for higher mass ones but not going over atomic number 92 can be around 1.5:1
example given is carbon-14

The conical flask is rinsed with water because if it was rinsed with acid, then the number of moles of acid in the conical flask would be too high. If it was rinsed with base, then the number of moles of acid would be too low.

It's 83, not 82.

Past 92 are transuranic elements.

 

[Haku]

I forget the real reason for the conical flask part
(I dont think i ever really questioned why the
conical flasks was rinsed with water, but
i know for sure that, that's the correct way)

the chemistry definition for unstable
has every element past 82
being radioactive / unstable
(your neutron to proton ratio is
correct)

in physics they mention every
transuranic element is radioactive/
or unstable, (meaning every element
greater than 92)

oh so i was confused. for chem, every element at atomics number greater than 82 is considered to be unstable. and 92 is just transuranic elements

but i remember another multiple choice question before saying that the conical flask is washed with water and used in titration with acid in burette. the answer was that the recorded acid would be too high cause of the conical flash being washed with distilled water.

 

[Haku]

The conical flask is rinsed with water because if it was rinsed with acid, then the number of moles of acid in the conical flask would be too high. If it was rinsed with base, then the number of moles of acid would be too low.

It's 83, not 82.

Past 92 are transuranic elements.

but the conical flask is gonna carry base. so if rinsed with water. the titration result for acid would be too high.

 

[serge]

oh so i was confused. for chem, every element at atomics number greater than 82 is considered to be unstable. and 92 is just transuranic elements

but i remember another multiple choice question before saying that the conical flask is washed with water and used in titration with acid in burette. the answer was that the recorded acid would be too high cause of the conical flash being washed with distilled water.

i think ive seen that one aswell
but i remember it being if you washed
it with base?

 

[Dreamerish*~]

but the conical flask is gonna carry base. so if rinsed with water. the titration result for acid would be too high.

Well, it carries either base or acid.

Still, having water in it does not alter the number of moles of acid or base it will hold.

Rinsing it with base or acid just defeats the whole purpose of measuring exactly 25 mL with a pipette.

Also, when you have half a drop of base/acid coming from the tip of the burette, you're instructed to wash it down with distilled water. Adding small amounts of water to the conical flask doesn't change anything.

 

[Haku]

gonna go call hsc help line now

 

[Haku]

lol, feel so stupid now.

anywayz. i finally get wat you were trying to tell me dreamerish. sorry

the number of moles on the conical flask dun change. so still need same amount of acid to titrate111zzz

 

[serge]

Rinsing it with base or acid just defeats the whole purpose of measuring exactly 25 mL with a pipette.

spot on... aslong as you keep twirling your conical flask
during the titration the water you rinsed the flask with
wont matter...
(since if you add 100ml of water and dont twirl your flask
your endpoint will be way off the real thing)