Question

calculate the no. of protons and neutrons in 9g of aluminum
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Answer 1

Answer:

1 mole of any substance weighs about its atomic or molecular mass,

Then 1 mole of Al weighs about 27u

X moles mole of Al weighs about 270u

x=

27

270

=10

Answer 2

Molar mass of Al = 27g/mol

No of moles = given mass / molar mass

                  = 9g/27gmol-1

                  = 0.33 mol  

OR  

Molar mass of Al = 27g/mol

27 g of Al = 1 mole          

So, 9g of Al = 1/27  x 9 mol

                   = 9/27 mol = 0.33 mol