Question

The gem emerald is a pure crystal of the mineral beryl, Be3Al2(SiO3)6 How many atoms of beryllium would be in 134.35 grams of beryl?

Answer 1

M(Be₃Al₂(SiO₃)₆) = 537.50 g/mol

n(Be₃Al₂(SiO₃)₆) $= \frac{134.35}{537.50}= 0.2499 \;mol$

Looking at the formula of beryl we can see that there are 3 moles of Beryllium in beryl so 1 one mole of beryl gives 3 moles of beryllium, 0.2499 moles of beryl give $0.2499 \times 3 = 0.7498$ moles of beryllium. One mole contains 6.022×10²³ elementary entities of the substance.

The number of atoms of beryllium $= 0.7498 \times 6.022 \times 10^{23} = 4.515 \times 10^{23} \;atoms$