Metal Ions- Sodium Hydroxide solution

Question 1

Why is sodium hydroxide used for the precipitation test?

Answer 1

The sodium hydroxide test works thanks to a precipitation reaction. Sodium hydroxide (NaOH) dissolves in solution to form sodium ions (Na+) and hydroxide ions (OH-). The hydroxide ions react with dissolved cations to form an ionic hydroxide salt, which precipitates out of solution.
When metal ions combine with the hydroxide ions (OH-) from either sodium hydroxide solution or ammonia solution, they form insoluble precipitates.

Question 2

What do the metal ions have to be in?

Answer 2

Solution

Question 3

What is a precipitate( insoluble salt)?

Answer 3

Insoluble salts are ionic compounds that are insoluble in water: the salt continues to exist as a solid rather than dissolving in the liquid.

Question 4

What do most transition metals produce?

Answer 4

Distinctive coloured precipitates

Question 5

How can you distinguish Aluminium ions from Calcium Ions and Magnesium Ions?

Answer 5

When sodium hydroxide is added to the compound with these ions, a white precipitate is formed.

If you carry on adding sodium hydroxide solution and the precipitate dissolves, this means the substance has aluminium ions.

Question 6

Copper(II)

Answer 6

Blue

Question 7

Iron(II)

Answer 7

Green

Question 8

Iron(III)

Answer 8

Brown

Question 9

Magnesium(2+)

Answer 9

White,insoluble

Question 10

Calcium(2+)

Answer 10

White,insoluble