Example: Explore the related properties of NaOH solids exposed to air.

(a), qualitative analysis:

The teacher showed the sodium hydroxide solid exposed to the air.

Q 1, composition of white solid; cause

2. Students design experiments to explore the composition of white material.

Students design experiments:

1, white material is Na2CO3 solid.

2. white material is a mixture of NaOH solid and Na2CO3 solid.

If white material is a Na2CO3 solid, how to prove it?

Students design experiments:

1, adding acid to produce gas (hydrochloric acid, dilute sulfuric acid, etc. )

2, salt precipitation (CaCl2 solution, Ca(OH)2 solution, etc. )

Teacher's guidance: Are CaCl2 _ 2 solution and Ca (OH) _ 2 solution the best answers?

Demonstration experiment 1, adding NaOH solution to Ca(OH)2 solution will produce precipitation.

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