For which of the following activities might you want to hire a chemist?
Answer: D. testing a rock sample for gold content
Which of the following procedures involves a physical change in one of the substances?
Answer: C. separating a salt solution by evaporating the water
Explanation:
Given parameters:
Number of molecules = 4.21 x 10²³ molecules
Unknown parameters:
Number of moles
Solution:
A mole can be defined as the amount of a substance that contains the avogadro's number of particles i.e 6.02 x 10²³
To find the number of moles:
Number of moles =
}[/tex]
Number of moles =
}{
}[/tex]
Number of moles of CaCl₂ = 0.699moles
Learn more;
mole calculation brainly.com/question/13064292
#learnwithBrainly