Question

Mr. Belland is setting up a lab that requires a solution of sodium hydroxide. This chemical comes in solid form and he has the option of large flakes or small pebbles. Which should he use to create his solution and why? What other things could he possibly do to speed up the dissolution of his solute?

Answer 1

• 1. Use small pebbles

• 2. Stir the solution

Step-by-step explanation:

He should use the material with the largest surface area to speed up the dissolution of the sodium hydroxide.

From the verbal description you migth infere that the small pebbles are small enough to permit a larger contact area than the large flakes.

In the first figure, I attach a picture of two samples of sodium hydroxide, to compare small pebbles and large flakes, showing precisely that the small granules should have a larger contact area than the larger flakes.

Thus, Br. Belland should use the small pebbles form to create his solution to have the greatest speed.

To speed up the dissolution, the other recomendation is to stir the solution. The factors that most affect the speed of dissolution are:

• The contact area
• Stirring
• Temperature.

The graph attached is the solubility curve for sodium hydroxide. It shows that it is more soluble at high temperatures, thus by raising the temperature you can dissolve more sodium hydroxide, but, since the dissolution of sodium hydroxide is largely exothermic, the temperature will raise any way and heating the solution could incrase the temperature more than desired, creating some risks. That is why I do not recommend to heat up the sodium hydroxide, but to stir the solution to speed up the dissolution.