Question

which alkali react with metals to realsed hydrogen gas

Answer 1

Hola mate...

When alkali (base) reacts with metal, it produces salt and hydrogen gas. Example: Sodium hydroxide gives hydrogen gas and sodium zincate when reacts with zinc metal.

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Answer 2

Just like acids, bases too react with an active metal to give a salt and hydrogen gas.

Alkalis like NaOH and KOH react with metals like zinc to give a salt and evolve hydrogen gas.

2NaOH + Zn ⇒ Na2ZnO2 + H2

The salt obtained here is sodium zincate.

2KOH + Zn ⇒ K2ZnO2 + H2

The salt obtained here is potassium tetrahydroxozincate.