Question

Calculate the mass of aluminium oxide
formed when 12.5 g g O2 reacts completely
with aluminium (atomic mass, 0-16, A1= 22)​

Answer 1

$\color{red}{\huge{\underline{\underline{GIVEN\dag}}}}$

• 12.5g of $O_{2}$ reacts completely with aluminium(Al).
• Atomic mass(M);

1. $O-16$
2. $Al-27$(u wrote wrong in question)

$\color{red}{\huge{\underline{\underline{SOLUTION\dag}}}}$

Balanced chemical equation;

$3Al+2O_{2}→2Al_{2}O_{3}$

Therefore,we know from equation;

3 moles of $Al$ and 2 moles of $O_{2}$ completely reacts to given 3 moles of $Al_{2}O_{3}$..........(1)

But,

12.5g of oxygen is given

We know that;

$\color{blue}{\boxed{mole(n)=\frac{weight}{M}}}$

Then;

Number of moles(n) of oxygen

$n = \frac{12.5}{16}$

$n = 0.78 \: \: moles.........(2)$

Therefore,from (1) & (2)

3 moles of Al............2 moles of $O_{2}$

? .............0.78 moles of $O_{2}$

$\implies \: n_{Al} = \frac{0.78 \times 3}{2}$

$\therefore\: n_{Al} = 11.7$

$weight_{Al}=n_{Al}×M$

$weight_{Al}=11.7×27$

$\color{orange}{\therefore weight(mass)_{Al}=315.9g}$

HOPE THAT HELPS!!