Question

1)Is it True or False: Samples must be cooled to room temperature before weighing. Explain your choice.

2)Describe why some ionic compounds dissolve in water while others do not.

3)Why should you not touch the crucible with your hands and use tongs instead whenever you weigh it.

Answer 1

True and false statement

1) Samples must be cooeld to room temperature before weighing : True

Otherwise it takes up moisture from air.

2) Some ionic solids dissolves in water whereas others do not. This deends upon the energy which is givesn off when the ions solubilizes in water. If this energy is greater than the energy required ot break of ionic interaction between the ions forming the ionic solid, the solid would dissociate in solution and dissolve. If however, the energy to dissociate or break ions apart is greater than the energy released by interaction with water, it will not dissociate and would not dissolve.

3) Touching the crucible with hands may contaminate it and may result in erroneous results. Thus it is necessary to alay use tongs.