Arun heated 2 g of ferrous sulphate crystals in a dry boiling tube.
(a) Mention two changes he observed while heating.
(b) What kind of chemical reaction is occurring?
(c) Identify the products formed in this reaction with the help of a balanced chemical equation.
(OR)
Pushpa took 3 𝑔 of copper powder in a china dish and heated it. She observed that the reddish brown surface of the copper powder becomes coated with a black substance. Based on her observation
(a) Identify the black substance.
(b) Explain the reason for the formation of black substance.
(c) Write the chemical equation of the reaction that takes place.
(d) Can the black coating on the surface be turned reddish brown? Explain.

Question

Accepted Answer

(a)When ferrous sulfate crystals are heated, the following two observations occur:

(i) A change in the state of color occurs.

(ii) during the process, a gas is generated.

(b) The reaction is a decomposition reaction since the compound decomposes into two or more substances.

(c) The chemical reaction is as follows;

$2 F e S O_{4} (s) + H e a t \to F e_{2} O_{3} (s) + S O_{2} (g) + S O_{3} (g)$

(OR)

(a) The black substance is a copper oxide $(C u O)$

(b) The black substance has been formed due to the oxidation of copper powder.
(c) The chemical reaction follows;

$C u O (s) + H_{2} (g) \to C u (s) + H_{2} O (l)$

(d) This black coating can be removed by treating the black compound with hydrogen.

Detailed Solution