[zeoblade]

I'm trying to figure out simple gas tests for the presence of nitrogen dioxide (NO₂) and nitric oxide (NO) but I can't find any.

NO₂ is a characteristic dark red-brown gas and soluble in water so I am wondering if I can suck it up in a pipette and bubble it through water to convert into ions and change the dark red-brown colour and use pH indicator to test for an acidic environment. But would this discriminate from other gases that might do the same thing? Maybe using an alkene that won't react with nitrate to discriminate it from bromine?

For NO, I was thinking using the glowing split to combust NO into NO2 and then precede as per procedure above, does anyone know of a better and simple method?

[JGK]

For NO₂ you could use fluorescein paper. Bromine will turn the paper pink, NO₂ doesn't.

http://books.google.ca/books?id=_tsm4ZXmGdwC&pg=PA136&lpg=PA136&dq=fluorescein+paper&source=bl&ots=v-a_r_y8tV&sig=XUhkM8k8Y2HERIjsoleUynfWEXc&hl=xx-elmer&ei=oAGIS7CFGY-oNpX1nNIO&sa=X&oi=book_result&ct=result&resnum=4&ved=0CA8Q6AEwAzgK#v=onepage&q=fluorescein%20paper&f=false

[skyjumper]

You don't really need the splint. NO reacts readily with air to make NO₂
per: 2 NO + O₂ → 2 NO₂

[zeoblade]

For NO₂ you could use fluorescein paper. Bromine will turn the paper pink, NO₂ doesn't.

http://books.google.ca/books?id=_tsm4ZXmGdwC&pg=PA136&lpg=PA136&dq=fluorescein+paper&source=bl&ots=v-a_r_y8tV&sig=XUhkM8k8Y2HERIjsoleUynfWEXc&hl=xx-elmer&ei=oAGIS7CFGY-oNpX1nNIO&sa=X&oi=book_result&ct=result&resnum=4&ved=0CA8Q6AEwAzgK#v=onepage&q=fluorescein%20paper&f=false

I forgot about fluorescein, thanks

You don't really need the splint. NO reacts readily with air to make NO₂ per: 2 NO + O₂ → 2 NO₂

Then I could use the colour of NO and NO₂ to resolve them and test for NO₂ as with fluorescein as JGK mentioned. Or maybe bubble NO₂ through an alkene and add AgNO₃ because if the dark re-brown gas was Br₂ instead of NO₂, AgBr would precipitate whereas adding NO₂ to an alkene won't precipitate AgNO₃. A bit more complicated than JGK's suggestion but I wonder if it's valid?

[zeoblade]

I was also wondering how to distinguish between these acid pairs:

(a) Hydrobromic or hydroiodic acid

Bubble Cl₂(g) through a solution of HI(aq) and will evolve I₂(g), which is purple in colour but through a solution if HBr(aq) will evolve Br₂(g) , which is brown in colour and will also layer above I₂(g) because it’s molecular weight is lighter. Test the pH because HI will have a stronger degree of dissociation than HBr because of its electronegativity

(b) Sulfuric or nitric acid

NH₃(g) + HNO₃(aq) --> NH₄NO₃(s)
Bubble NH₃(g) through HNO₃(aq) will give NH₄NO₃(s), which is an explosive.

NH₃(g) + H₂SO₄(aq) --> (NH₄)₂SO₄(s)
But bubble NH₃(g) though H₂SO₄(aq) will give (NH₄)₂SO₄(s), which is a flame retardant.

(c) Hydrochloric or acetic acid?

HCl(aq) +  AgNO₃(aq) --> AgCl₂(s) + HNO₃(aq)
Mix with AgNO₃(aq) to precipitate a metal salt, AgCl₂(s), that can be heated to produce silver metal and pale yellow-green chlorine gas.

CH₃COOH(aq) + AgNO₃(aq) --> CH₃COOAg(s) + HNO₃(aq)
Mixing with AgNO₃(aq) to precipitate a metal acetate, CH₃COOAg(s), that won’t produce metallic silver or a pale yellow-green gas when heated but will give an offensive taste in the presence of cigarette smoke.