And hello to whoever is here, I still have a few more
MCQ questions to ask
1. When testing for a chloride ion using silver nitrate, the
solution must be acidified with dilute nitric acid. What is the
purpose of the nitric acid? (won't type out the whole options, just
the one I chose and the one given by the marking scheme. the
underlined choice
is the one provided by TYS)
A to prevent precipitation of silver carbonate
B to oxidise the
chloride ion.
2. Which statement about the ions of the group VII elements is
correct
I chose the option of
All the ions contain more electrons than protons. (Of course,
they gain e- to form the ions)
Ans gave all the ions have 7 electrons in outer shell
(thought this's talking about the atoms not ions)
3. Which gas is evolved when an alkaline solution of NaNO3 is
warmed with Al
I chose ammonia (well isnt this test for NO3- ions?) answer is a
crappy NO2.
4 These reactions are used in the manufacture of H2SO4
P S+O2 -> SO2
Q 2SO2 + O2 (reversible rxn) ->
2SO3
R SO3 + H2O -> HSO4
Which reactions are speeded up by using a catalyst? (not very
sure about this. can someone tell me how to identify if a reaction
requires a catalyst or not?)
anyway only reaction B requires a catalyst according to the
answer given
Lastly
2 strips of different metal strips are fastened together
and immersed in a beaker of HCl acid. The strips are of the same
size. After 5 mins, which beaker contains the least amount of Zn
ions
Mg and Zn strip
Pb and Zn strip
Fe and Zn strip
Ag and Zn strip
I chose Mg and Zn strip because Mg will react in place of Zn and
hence prevent Zn from being oxidised to Zn2+. But the answer is
also another crappy and unexplanable Fe and Zn strip.
Not sure if TYS answers these days are reliable. Cuz my teacher
said there's one physics (or chemistry, can't remember) TYS MCQ
that contains 10 wrong answers. Shocking. Haha. Anyway, I am not
very sure of question 1 and 4. The rest of the answers look fine to
me.
Whatever the case, please help me check if i got the right
choices. Thank you.
1) Where do u even get the carbonate ion from?
2) Unsure about this but the answer would be right if its atom
as u say.
3) Only NH4 compounds will give off NH3 gas. Just look at the
structure of the compound and see what is the only gas possible to
be given out from it.
4) B? Q is the 1 that needs a catalyst since its a reversible
reaction. If no catalyst is used to increase the rate of the
reaction, your entire process is held up in this reaction as part
of the SO3 will go back to SO2 and O2.
5) For such experiments, the closer the 2 metals are in the
reactivity series, the less is the potential difference between
them and thus the slower the reaction.