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24.
For analyzing the concentration of lead in drinking water samples, a chemist needs to make 600 ml
of 0.1 M potassium bromide (KBr, molar mass=119 g/mole). Which of the following is the most
accurate determination of the mass of KBr that he needs to weigh out?

A5.04 g
B.3.0g
C. 7.1g
D. 11.9g

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.

since electrons are negative the answer is neagtaive