When making copper sulfate from copper oxide, the solid copper oxide must be added to the acid in excess i. e. there will be some unreacted
copper oxide left in solution). This is because this base is... whar?

insoluble
alkaline
acidic
neutral
soluble

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.

the correct answer to this question is 2

answer; 4 electrons;