Which of the following does not increase the rate at which a solid dissolves in water?

a. raising the temperature of the water

b. stirring the solution

c. using large pieces of the solid

d. crushing the solid

Option c. using large pieces of the solid

Explanation:

There are two general ways of increasing the rate at which a solid (solute) dissolve in water (a solvent):

stirring the solution; because in this way the dissolved particles will move away more quickly from the contact surface.

increasing the surface area of the solute, to increase the contact between the solute and the solvent.

Increasing the temperature may or not lead to an increase in the rate at which a solid dissolves in water. Many substances are more soluble in hot water than in cold water, so raising the temperature, although not valid for all the solids, certainly works fine to increase the temperature of many solids.

Examine each choice.

a. raising the temperature of the water:

Incorrect. As already stated, it increase the rate at which many solids dissolve in water, so you can not tell that it does not increase the rate at which a solid dissolves in water.

b. stirring the solution:

Incorrect. As stated, this is a common way to increase the rate at which a solid dissolves in water.

c. using large pieces of the solid:

Correct. Using large pieces of the solid does not increase the rate at which a solid dissolves in water, since large chunks of the solute will less surface contact with the solvent (water) leading to the opposite effect of decreasing the rate at which the solids gets dissolved.

d. crushing the solid

Incorrect. Indeed, crushing the solid incfreases the surface contact between it and the solven, so this will increase the rate at which it dissolves.