Re: Qualitative analysis - group 1 cations lab
What single reagent could you add that would allow you to differentiate between the members of each pair of solid compounds below? Tell what happens to each substance when the reagent is added and show a balanced net ionic equation wherever a reaction occurs.
1. NH4Cl and AgCl
2. PbI2 and KI
Please help with the all three questions: What single reagent, tell what happens, show a balanced net ionic equation
isn't silver carbonate non soluble?
What about lead sulfate?
Ah, the joy of qualitative analysis! Let's dive into it with a splash of humor, shall we?
1. For differentiating NH4Cl and AgCl, you can add none other than good old sodium hydroxide (NaOH). When you mix NaOH with NH4Cl, it'll bubble up, giving off a smell that reminds you of those sneezy cleaning products. This is because ammonia gas (NH3) is formed:
NH4Cl + NaOH → NH3 + H2O + NaCl
But when you mix NaOH with AgCl, it's a totally different story! No bubbles, no sneezing. Instead, you'll see a lovely, shiny, silver precipitate, indicating the formation of silver hydroxide (AgOH):
AgCl + NaOH → AgOH + NaCl
2. Now, for the thrilling duo of PbI2 and KI, our reagent in shining armor is none other than lead(II) nitrate (Pb(NO3)2). Brace yourself for some color-changing fun!
When you mix Pb(NO3)2 with KI, a vibrant yellow precipitate will appear with a touch of elegance. That's lead(II) iodide (PbI2) showing off its stylish side:
Pb(NO3)2 + 2KI → PbI2 + 2KNO3
So, there you have it! With a little chemistry and a splash of humor, you can differentiate between these pairs of solid compounds. Just be sure to wear a lab coat and your best clown shoes while you're at it! Remember, science and laughter go hand in hand.
1. To differentiate between NH4Cl and AgCl, you can add dilute ammonia solution (NH3).
When dilute ammonia solution is added to NH4Cl, a white precipitate of NH4Cl is formed. This indicates the presence of NH4+ ions.
NH4Cl (aq) + NH3 (aq) → NH4+ (aq) + Cl- (aq) + NH4Cl (s)
Net ionic equation: NH4+ (aq) + Cl- (aq) → NH4Cl (s)
When dilute ammonia solution is added to AgCl, a light brown precipitate of AgCl dissolves to form a colorless complex ion, [Ag(NH3)2]+. This indicates the presence of Ag+ ions.
AgCl (s) + 2NH3 (aq) → [Ag(NH3)2]+ (aq) + Cl- (aq)
Net ionic equation: Ag+ (aq) + Cl- (aq) → [Ag(NH3)2]+ (aq)
2. To differentiate between PbI2 and KI, you can add a solution of concentrated sulfuric acid (H2SO4).
When concentrated sulfuric acid is added to PbI2, a yellow precipitate of PbSO4 is formed. This indicates the presence of Pb2+ ions.
PbI2 (s) + H2SO4 (aq) → PbSO4 (s) + 2HI (aq)
Net ionic equation: Pb2+ (aq) + SO4^2- (aq) → PbSO4 (s)
When concentrated sulfuric acid is added to KI, no reaction occurs. This indicates the absence of any significant reaction between KI and the reagent.
KI (s) + H2SO4 (aq) → No Reaction
To differentiate between the members of each pair of solid compounds, you need to identify a single reagent that would cause a reaction with one compound but not the other.
1. NH4Cl and AgCl: The reagent you can use is aqueous ammonia (NH3). When NH3 is added to NH4Cl, no visible reaction occurs. However, when NH3 is added to AgCl, a white precipitate of Ag(NH3)2+ is formed. The balanced net ionic equation for this reaction is as follows:
AgCl(s) + 2NH3(aq) → Ag(NH3)2+(aq) + Cl^-(aq)
2. PbI2 and KI: The reagent you can use is concentrated nitric acid (HNO3). When HNO3 is added to PbI2, no visible reaction occurs. However, when HNO3 is added to KI, a yellow precipitate of iodine (I2) is formed due to the reaction with KI. The balanced net ionic equation for this reaction is as follows:
2KI(aq) + HNO3(aq) → I2(s) + 2KNO3(aq) + H2O(l)
In summary, by adding aqueous ammonia to NH4Cl and AgCl, you can differentiate them based on the formation of a white precipitate with AgCl. And by adding concentrated nitric acid to PbI2 and KI, you can differentiate them based on the formation of a yellow precipitate with KI.