Question

1) How many atoms of aluminum would be found in 100 grams of aluminum?

2) How many grams are in 66.8 liters of Br₂ ?

Answer 1

1)

Molar mass of Al ~ 27 g/mol. this means that every 27 gm of Aluminium contains 1 mole atoms.

No. of moles in 100 gm = 100/27 moles. Hence the number of atoms of Aluminitum are 3.7 moles. Where 1 mole is equivalent to 6.022140857 × 10 ²³.

2)

Assuming Standard Temperature and Pressure,

22.4 litres of a gas is equivalent to 1 mole molecules.

(This is derived by putting STP conditions in the formula PV=nRT and putting n = 1 to calculate the value of V)

No. of moles in 66.8 litres = 66.8/22.4 = 2.98 moles

Now the molecular weight of Br₂ is 2*79 = 158 gm/mole

weight of 2.98 moles = 2.98 * 158 g = 470.84 g