Question

Which of the following turns lead acetate paper black?
A $S{O_2}$
B. $S{O_3}$
C. ${H_2}S$
D. ${H_2}S{O_4}$

Answer 1

The gas which turns lead acetate paper black is a colorless gas with rotten egg smells. It is very poisonous, corrosive in nature. It is also known as sour gas or sewer gas. Its molecular weight is 34.08 g/mol

Complete step by step answer:
Lead acetate is the chemical compound also known as lead (II) acetate. It is a white crystalline in texture having a molecular formula $Pb{({C_2}{H_3}{O_2})_2}$. It is formed reacting acetic acid on litharge.
The lead acetate reacts with different gases to form product of different property.
Lead acetate reacts with sulfur dioxide to form lead (IV) hyposulfite and acetate ion.
The reaction between lead acetate and sulfur dioxide is shown below.
$Pb{(C{H_3}COO)_2} + S{O_2} \to Pb{(S{O_2})_2} + {(C{H_3}COO)_2}$
This reaction is a type of double displacement reaction.
Lead acetate on reacting with hydrogen sulfide gives black color compound called lead sulfide and succinic acid.
The reaction between lead acetate and hydrogen sulfide is shown below.
$Pb{(C{H_3}COO)_2} + {H_2}S \to PbS + C{H_3}COOH$
It is type of precipitation reaction where lead sulfide forms a black precipitate.

Lead acetate on reacting with sulfuric acid gives solid lead sulfate and acetic acid.
The reaction of lead acetate with sulfuric acid is shown below.
$Pb{(OCOC{H_3})_2} + {H_2}S{O_4} \to Pb(S{O_4}) + 2C{H_3}COOH$
This is a type of precipitation reaction, where solid lead sulfate precipitate outs.
Thus, among all the given gas hydrogen sulfide ${H_2}S$ turns lead acetate paper black.

Therefore, the correct option is C .

Note: The lead acetate paper is used to test the presence of sulfur in the compound. The test is positive when the paper changes to black or brown.