CHEMISTRY PAPER 1 HERE

[aquarian93]

is a burette is used for a very accurate amount compared to a pipette?

[aquarian93]

this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D

y cnt it b C? pls help, thanks in advance

[MR.BooMBastiC]

burette!!!!!!

i did in 1 of da  past pprs

[esso]

pippete is to measure fixed volumes...like 25 cm3 or 30 cm3

but burrete is vry accurate ,when compared with m.cylinder,and its used to measure varying volumes,like 35.5 or 47.2

hope i helped...

[nid404]

An aqueous solution contains barium iodide.
It is possible to obtain a solution that contains Ba2+(aq) but no I–(aq) by adding ……1…… until no
more ……2…… precipitate forms.

Which words correctly complete gaps 1 and 2?
1                                             2
A aqueous lead(II) nitrate         white
B aqueous lead(II) nitrate         yellow
C dilute sulphuric acid               white
D dilute sulphuric acid               yellow


help please...need an explanation..

U omit C and D first cuz if u want barium ions in the solution that reacting it with acid gives sulphate which is not soluble.
Since u want barium ions to be in the solution, u want iodide to precipitate so that it can be filtered. So u add Lead nitrate and this will react with barium iodide to give barium nitrate and lead iodide(which is yellow). lead iodide can be filtered as it is insoluble and will precipitate. the solution will contain no iodide ions.

I hope it's clear...

[....]

this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D

y cnt it b C? pls help, thanks in advance

For 3, there would be no loss in mass, as any gas produced would remain inside the conical flask, and not be able to excape through the stopper.

[nid404]

nd one more question

which process can convert molecules to a new substance by removing hydrogen atoms
A displacement
B fermentation
C neutralisation
D oxidation

how do you solve this question

john it is oxidation By the way it is not der 4r us it cums in O-levels loss of hydrogen is oxidation

Just didn't strike my mind...thanx for reminding and moreover for helping john

[esso]

An aqueous solution contains barium iodide.
It is possible to obtain a solution that contains Ba2+(aq) but no I–(aq) by adding ……1…… until no
more ……2…… precipitate forms.

Which words correctly complete gaps 1 and 2?
1                                             2
A aqueous lead(II) nitrate         white
B aqueous lead(II) nitrate         yellow
C dilute sulphuric acid               white
D dilute sulphuric acid               yellow


help please...need an explanation..

U omit C and D first cuz if u want barium ions in the solution that reacting it with acid gives sulphate which is not soluble.
Since u want barium ions to be in the solution, u want iodide to precipitate so that it can be filtered. So u add Lead nitrate and this will react with barium iodide to give barium nitrate and lead iodide(which is yellow). lead iodide can be filtered as it is insoluble and will precipitate. the solution will contain no iodide ions.

I hope it's clear...

ya crystal clear...Thanks for d help...

[dondon93]

Guys please help with this,...
When lithium reacts with water, if forms lithium oxide + hydrogen OR it forms lithium  hydroxide + hydrogen?
And which metals react with water to form  metal oxide + hydrogen and which ones react with water to form metal hydroxide + hydrogen???
Help please???

[Bani]

Please help.....O/N 2007, paper 1, Q11
please explain, thanks in advance...

[aquarian93]

this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D

y cnt it b C? pls help, thanks in advance

For 3, there would be no loss in mass, as any gas produced would remain inside the conical flask, and not be able to excape through the stopper.

yea bt if it dusnt escape, u can still use it cuz the mass will increase as gas is produced and wont escape. da mass will increase
rite?

[esso]

its neutrilisation rite....cause hydrogen is removed from acids when reacting with bases

[nid404]

Guys please help with this,...
When lithium reacts with water, if forms lithium oxide + hydrogen OR it forms lithium  hydroxide + hydrogen?
And which metals react with water to form  metal oxide + hydrogen and which ones react with water to form metal hydroxide + hydrogen???
Help please???

Lithium is a group 1 metal so it forms hydroxide and hydrogen

Group 2 metals react to form metal oxide and hydrogen(but magnesium reacts with steam to give hydroxide

Metals below hydrogen in reactivity do not form either.

[girl_92]

this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D

y cnt it b C? pls help, thanks in advance

u cannot take 3 bcoz a stopper will not allow the gas to escape n the two methods loss of mass wid time n amount of gas collected by the passage time are used in 2 n 4

[....]

this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D

y cnt it b C? pls help, thanks in advance

For 3, there would be no loss in mass, as any gas produced would remain inside the conical flask, and not be able to excape through the stopper.

yea bt if it dusnt escape, u can still use it cuz the mass will increase as gas is produced and wont escape. da mass will increase
rite?

Umm no, conservation of mass = mass of products is always equal to mass of reactants. So, to show the rate of reaction, a decrease in mass must occur.