how many moles are in 15.0 grams of silicon powder??

Question

And can you show me how you solve it??

also this one too:

how many atoms are contained in 1.65 moles of copper metal?

Answer 1

First, find the molar mass of silicon powder.
The equation will be as follows:

15.0g x 1 mol (over) molar mass = your answer

Answer 2

atomic mass of Silicon is 28. (read off from the periodic table)
therefore 1 mole of Silicon is 28 g.
15 grams of silicon would be 0.54 moles.

1 moles of copper is 6 x 10^23* copper atoms.
so, 1.65 moles of copper contains 9.9 x 10^23 copper atoms.

*Google for Avogadro's number or Avogadro's constant for more info.

Answer 3

If it is pure silicon, the atomic mass is 28.09 grams/mole. In 15 grams there are then 15/28.09 moles

One mole of any substance has Avogadro number (= 6*10^23) of atoms (or molecules). 1.65 moles has 1.65*Avogadro number = 1.65*6*10^23 atoms