Choose the correct statements about the hydrides of group 15 elements.

A. The stability of the hydrides decreases in the order $$\mathrm{NH}_3>\mathrm{PH}_3>\mathrm{AsH}_3> \mathrm{SbH}_3>\mathrm{BiH}_3$$.

B. The reducing ability of the hydride increases in the order $$\mathrm{NH}_3<\mathrm{PH}_3<\mathrm{AsH}_3 <\mathrm{SbH}_3<\mathrm{BiH}_3$$.

C. Among the hydrides, $$\mathrm{NH}_3$$ is strong reducing agent while $$\mathrm{BiH}_3$$ is mild reducing agent.

D. The basicity of the hydrides increases in the order $$\mathrm{NH}_3<\mathrm{PH}_3<\mathrm{AsH}_3< \mathrm{SbH}_3<\mathrm{BiH}_3$$.

Choose the most appropriate from the options given below :

Given below are two statements :

Statement (I) : The gas liberated on warming a salt with dil $$\mathrm{H}_2 \mathrm{SO}_4$$, turns a piece of paper dipped in lead acetate into black, it is a confirmatory test for sulphide ion.

Statement (II) : In statement-I the colour of paper turns black because of formation of lead sulphite. In the light of the above statements, choose the most appropriate answer from the options given below :

The Lassiagne's extract is boiled with dil $$\mathrm{HNO}_3$$ before testing for halogens because,

On passing a gas, '$$\mathrm{X}$$', through Nessler's regent, a brown precipitate is obtained. The gas '$$\mathrm{X}$$' is