Question
Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?
✓
Answer
While testing the Lassaigne’s extract for the presence of halogens, it is first boiled with dilute nitric acid. This is done to decompose NaCN to HCN and Na2S to H2S and to expel these gases. That is, if any nitrogen and sulphur are present in the form of NaCN and Na2S, then they are removed. The chemical equations involved in the reaction are represented as
NaCN + HNO3 → NaNO3 + HCN
Na2S + 2HNO3 → 2NaNO3 + H2S
NaCN + HNO3 → NaNO3 + HCN
Na2S + 2HNO3 → 2NaNO3 + H2S
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
Calculate the energy required for the process,
$\text{He}^+(\text{g})\rightarrow\text{He}^{2+}\text{(g)}+\text{e}^-$
The ionization energy for the H atom in the ground state is 2.18 × 10–18J atom–1
→$\text{He}^+(\text{g})\rightarrow\text{He}^{2+}\text{(g)}+\text{e}^-$
The ionization energy for the H atom in the ground state is 2.18 × 10–18J atom–1
How much energy is required to ionise a H atom if the electron occupies n = 5 orbit? Compare your answer with the ionization enthalpy of H atom (energy required to remove the electron from n = 1 orbit).
Write the anode reaction, the cathode reaction and the net cell reaction in the following cells. Which electrode would be positive terminal in each cell?
→- $\text{Zn}\text{(s)}|\text{Zn}^{2+}||\text{Br}_2|\text{Br}^-|\text{Pt}\text{(s)}$
- $\text{Cr}\text{(s)}|\text{Cr}^{3+}||\text{I}_2|\text{I}^-|\text{Pt}\text{(s)}$
- $\text{Pt}\text{(s)}|\text{H}_2\text{(g)}||\text{H}^+\text{(aq)}||\text{Cu}^{2+}|\text{Cu}\text{(s)}$
- Why is NH4Cl added before addition of NH4OH in qualitative analysis of 3rd group?
- Which will be added to precipitate soap
(RCOONa)? NaCl or KCl and why?'
Write bond line formulas for: Isopropyl alcohol, 2,3-Dimethylbutanal, Heptan-4- one.
Give the electronic configuration of the transition elements. Write their four important characteristics.
How can you predict the following stages of a reaction by comparing the value of Kc and Qc?
- Net reaction proceeds in the forward direction.
- Net reaction proceeds in the backward direction.
- No net reaction occurs.
For the following bond cleavages, use curved-arrows to show the electron flow and classify each as homolysis or heterolysis. Identify reactive intermediate produced as free radical, carbocation and carbanion.
What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the following species:
$\text{HNO}_2,\text{CN}^-,\text{HClO}_4,\text{F}^-,\text{OH}^-,\text{CO}_3^{2-}\text{and S}^{2-}$
→$\text{HNO}_2,\text{CN}^-,\text{HClO}_4,\text{F}^-,\text{OH}^-,\text{CO}_3^{2-}\text{and S}^{2-}$
Calculate the pH of the resultant mixture :
10 mL of $0.1 M H _2 SO _4+10 mL$ of 0.1 M KOH
→10 mL of $0.1 M H _2 SO _4+10 mL$ of 0.1 M KOH