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2.5 * 6.02 * 10^23    hope i helped

One mole substance there are [tex]6.02 \times10^2^3[/tex] elementary chemical entity present.  1.5 moles of Helium, there are  [tex]\bold{9.03 \times 10^2^3}[/tex] atoms present.

Mole Concept:

In one mole substance there are [tex]6.02 \times10^2^3[/tex] elementary chemical entity present.

  • This number is as many as Carbon atoms present in 12g of Carbon 12.
  • [tex]6.02 \times10^2^3[/tex] is also known as Avogadro's constant.

As we know 1 mole = [tex]6.02 \times10^2^3[/tex]

hence,

1.5 moles of Helium = [tex]1.5 \times 6.02 \times10^2^3 = \bold{9.03 \times 10^2^3}[/tex]

Therefore we can conclude that in 1.5 moles of helium, there are  [tex]\bold{9.03 \times 10^2^3}[/tex] atoms present.

To know more about mole concept, refer to the link:

https://brainly.com/question/12805690