Question

How many number of aluminium ions are present in$0.051g$ of aluminium oxide?

• A. $6.023 \times 10^{20}$
• B. 3 ions
• C. $6.023 \times 10^{23}$
• D. 9 ions

Answer 1

Answer: (A)

$6.023 \times 10^{20}$

Answer 2

(1) : mass of $Al_{2}O_{3} = 2 \times 27 + 3 \times 16 = 102$

$0.051g$of $Al_{2}O_{3} = \frac{0.051}{102} = 0.0005$mol

1 mol of $Al_{2}O3$contains $2 \times 6.023 \times 10^{23}Al^{3 +}$ions

$0.0005$mol of $Al_{2}O_{3}$contains $2 \times 0.0005 \times 6.023 \times 10^{23}Al^{3 +}$ions

=$6.023 \times 10^{20}Al^{3 +}$ions