1.51 Consider the following separations of materials. State whether a physical p
ID: 573754 • Letter: 1
Question
1.51 Consider the following separations of materials. State whether a physical process or a chemical reaction is in- volved in each separation. a Sodium chloride is obtained from seawater by evapo- ration of the water Mercury is obtained by heating the substance mercury(II) oxide; oxygen is also obtained. Pure water is obtained from ocean water by evaporat- ing the water, then condensing it. Iron is produced from an iron ore that contains the substance iron(III) oxide. Gold is obtained from river sand by panning (allowing the heavy metal to settle in flowing water)Explanation / Answer
a) Sodium chloride is obtained by evaporation of sea water. Sodium chloride and sea water are different chemical species. On condensing the water, the mixture of sodium chloride and sea water can be reformed. This process is a physical process since the mixture can be simply obtained by cooling sodium chloride and sea water.
b) The process is a chemical reaction since mercury (II) oxide decomposes or breaks down into mercury and oxygen. Simply cooling mercury and oxygen (cooling is the reverse process of applying heat) will not regenerate mercury (II) oxide.
c) The process is a physical process. The process can be easily reversed to obtain the mixture. In other words, pure water and sea water can be easily mixed to form a mixture.
d) The process is a chemical reaction. Iron (III) oxide and iron are two different substances having entirely different physical and chemical properties.
e) The process is a physical process. Gold separates out from river water by sedimentation. Gold and river water can be stirred again to obtain the mixture.
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