Question

15. Select the correct statements. (1) Magnesium ribbon on heating in air catches fire and burns with white flame to form magnesium oxide. (ii) All metals react with water to evolve hydrogen gas. (iii) Iron reacts with cold water slowly. (iv) Sodium metal is always kept in kerosene as it reacts vigorously with air and moisture. (A) (i) and (iii) only (B) (i) and (iii) only (C) (i) and (iv) only (D) (ii) and (iv) only​

Answer 1

Final Anwer: Option C

Statements:

⇒ Magnesium ribbon on heating in air catches fire and burns with white flame to form magnesium oxide.

⇒ All metals react with water to evolve hydrogen gas.

⇒ Iron reacts with cold water slowly

⇒ Sodium metal is always kept in kerosene as it reacts vigorously with air and moisture

Answer:

First statement = True

Second statement = False

Third statement = False

Fourth statement = True

Therefore, correct answer is option (C)

Explanations:

⇒⇒ For the first one it is true, magnisium ribbon which is silvery white (grey) in colour will burn with a dazzling white flame leaving a residue called magnisium oxide (MgO) which is a white powder.

⇒⇒  For the second statement, it is false. Although most of the metals react with water to evolve hydrogen gas along with the formation of metal hydroxide.Some metals react with the gaseous form of water called steam. Some metals do not react with water at all. Like gold, silver etc..Therefore this statement is considered false

⇒⇒ For the third, it is also false, since iron does not react with neither cold water nor hot water. It only reacts with steam to form Ferric Oxide.

⇒⇒ For the fourth, it is true, infact sodium (Na) is the second most reactive metal after potassium. Sodium metal reacts violently and vigorously with air and moisture and therefore it is kept in kerosene to avoid contact with air and moisture.