A piece of metal (M) is dissolved in nitric acid and the resulting solution is treated with a small quantity of sodium hydroxide to produce a white precipitate (B) which redissolves on the addition of excess alkali. The precipitate (B)when ignited in a crucible produces the oxide of the metal(m). The METAL M is

omgimd

1 year ago

Metal (M) in Nitric Acid: This tells us the metal is reactive enough to dissolve in nitric acid (HNO₃). This rules out very unreactive metals like gold (Au).
White Precipitate (B) with Sodium Hydroxide (NaOH): This indicates the formation of a metal hydroxide. Many metal hydroxides are insoluble and form precipitates.
Precipitate Redissolves in Excess Alkali: This is a crucial clue! It means the metal hydroxide is amphoteric. Amphoteric hydroxides dissolve in both acids and bases.
Precipitate (B) Ignited Produces Metal Oxide: This is a typical reaction for metal hydroxides. When heated strongly, they decompose to form the metal oxide and water.
Applying the Clues:

Zinc (Zn):
Zinc dissolves in nitric acid.
Zinc hydroxide (Zn(OH)₂) is a white precipitate.
Zinc hydroxide is amphoteric, meaning it redissolves in excess NaOH
Zinc hydroxide decomposes to zinc oxide (ZnO) when heated

paschalcharles

4 years ago

please explain, I don't understand

Jessica2010

1 year ago

Thank you

teekeysOfficial

2 months ago

A pice of metal M is dissolved in nitric acid which is HNO3 and the resulting solution is treated with small quantity of NaOH to produce white precipitate.

Now, for the metal to dissolve to produce a precipitate, then it is reactive so therefore option D is out of it.

The precipitate is white then Cu is out of it because it forms a blue precipitate with NaOH.

Ca is also out of it because its precipitate is usually insoluble in excess of NaOH which is one of the properties of Group 2 elements.

We are hereby left with Al and Zn.

Al, due to the fact that it's ampotheric, it does not react with HNO3 either comcentrated or dilute. It forms a protective layer of Al2O3 (aluminum oxide) which is why HNO3 is usually transported in aluminum containers.

Zn is the answer left and it satisfied all that was stated. Therefore the answer is option A.

Mind you, Fe does not react with HNO3 also.

OG_Loc

1 year ago

choking 💀

blackcougar8

1 year ago

The correct answer is: C. Al (Aluminium)

Explanation:

When aluminium (Al) reacts with nitric acid, it forms aluminium nitrate, a soluble salt.

Adding a small amount of sodium hydroxide (NaOH) to the solution gives a white precipitate of aluminium hydroxide (Al(OH)₃).

This white precipitate redissolves in excess NaOH to form a soluble complex, [Al(OH)₄]⁻, showing amphoteric behavior (can react with both acids and bases).

When aluminium hydroxide is ignited (heated strongly), it decomposes to form aluminium oxide (Al₂O₃).


Other options:

Zn also shows amphoteric behavior, but its hydroxide is not always distinctly white and the reaction profile differs.

Cu gives blue solutions and black CuO on heating.

Au doesn't react easily with nitric acid.

Ca forms a white precipitate but it doesn’t redissolve in excess NaOH.


So, Aluminium (C) fits all the observations best.