A soft metal (A) gives a violet flame test. When burnt in excess , (A) gives chrome yellow powder (B) which on reaction with water gives alkaline solution (C) and , (A) gives chrome yellow powder (B) which on reaction with water gives alkaline solution (C) and . Identify A and B.

Solution:

concept - All alkali metals (Lithium, sodium, potassium, Rubidium and Cesium) are soft and can be cut by a knife.
Alkali metals react with oxygen to produce their oxides.
Lithium oxide is the lightest alkali metal oxide and a white solid.
Sodium oxide is a white solid
Potassium oxide is a pale-yellow solid.
Rubidium oxide is a yellow solid.
Cesium oxide is a yellow-orange solid.
Now, a soft metal which gives violet flame test is potassium, K.

So, B is potassium oxide.

So, C is potassium hydroxide.
Hence, the correct answer is 3.

Solution:

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