Year 12s: what will be the first way you research your future options? >>

Help with a few questions please?

'State what is observed when conc. sulphuric acid reacts with solid sodium chloride
Write an equation for the reaction occurring'

No idea as to what products this might make.

'State the reagents which could be used to convert aqueous chromium(III) ions into chromate(VI) ions.'

For this one, I already have H2O2, but need a second one.

'State what is observed when sodium carbonate is added to an aqueous solution of aluminium chloride'

Here, I have CO2 bubbles as one, but need another.
It's not [Al (H2O)3 (OH)3] precipitate is it?

Any help would be appreciated

Reply 1

EierVonSatan

i) H2SO4 + 2NaCl ---> Na2SO4 + 2HCl => see HCl fumes

ii) Not sure - maybe potassium permanganate?

iii) Al³⁺_(aq) is acidic, acid + carbonate ---> salt + water + CO2 => see bubbles

Reply 2

chemicalguy

Q2 alkaline H2O2 so NaOH

Reply 3

pompeyspud

EierVonSatan

i) H2SO4 + 2NaCl ---> Na2SO4 + 2HCl => see HCl fumes

ii) Not sure - maybe potassium permanganate?

iii) Al³⁺_(aq) is acidic, acid + carbonate ---> salt + water + CO2 => see bubbles

For i.), is the H2SO4 acting as an oxidising agent? The Na is +1 in NaCl and +2 in the Na2SO4 right? Or not?

Reply 4

EierVonSatan

chemicalguy

Q2 alkaline H2O2 so NaOH

ooh they wanted the other component of the oxidising mixture, not another oxidant - d'oh

pompeyspud

For i.), is the H2SO4 acting as an oxidising agent? The Na is +1 in NaCl and +2 in the Na2SO4 right? Or not?

Reply 5

charco

Study Forum Helper

pompeyspud

For i.), is the H2SO4 acting as an oxidising agent? The Na is +1 in NaCl and +2 in the Na2SO4 right? Or not?

no, no change in oxidation numbers

Reply 6

pompeyspud

Oh, well then why is it asking me its role? It's not something blindingly stupidly obvious, like catalyst or something is it?

Reply 7

charco

Study Forum Helper

pompeyspud

Oh, well then why is it asking me its role? It's not something blindingly stupidly obvious, like catalyst or something is it?

It's behaving as a strong acid and displacing a more volatile acid from one of its salts - it is forcing the Cl- ions of the NaCl to accept a proton and become hydrogen chloride molecules

Reply 8

pompeyspud

charco

It's behaving as a strong acid and displacing a more volatile acid from one of its salts - it is forcing the Cl- ions of the NaCl to accept a proton and become hydrogen chloride molecules

That seems a little complicated for an AQA Mod 5 two marker question. Nothing like a Lewis or Bronsted-Lowry acid is it?

Reply 9

pompeyspud

Ah well, it's only two marks. Thanks for all the help!

Reply 10

chemicalguy

pompeyspud

Ah well, it's only two marks. Thanks for all the help!

The context of this one for AQA is the strength of halide as a reducing agent - Cl- is too weak to reduce S in H2SO4 and its compared with Br- and I-. The faca is acting as a BL acid does nt concern them other than you get misty white fumes and no colour change. That's the lots as far as AQA are concerned - its AS mod 2