Calculate the number of atoms in a 0.123-gram sample of aluminum foil.
Answers
Explanation:
The key to this problem is the correct interpretation of what atomic weight means.
Notice that aluminium is said to have an atomic mass of 26.982 u. The unit used here is the unified atomic mass unit, u.
The unified atomic mass unit is defined as 112th of the mass of a neutral carbon-12 atom and is approximately equal to the mass of one nucleon, as in the mass of one proton or one neutron. Also, you should know that you have
1 ux=x1 g/mol
This means that the mass of one mole of aluminium atoms will be 26.982 g.
As you know, one mole of any element contains exactly 6.022⋅1023 atoms of that element.
This means that if you know how many moles of aluminium you have in 4.55 g, you can use Avogadro's number to find the number of atoms.
4.55g⋅1 mole Al26.982g=0.168631 moles Al
Therefore, you will have
0.168631moles of Al⋅6.022⋅1023atoms of Al1mole Al=1.02⋅1023atoms of Al
The answer is rounded to three sig figs, the number of isg figs you gave for the mass of the sample.
mark me as Brainliest