Question

How many grams of oxygen will be required to react completely with 27g of Al?

Answer 1

24 g

Answer 2

Solution:

1. Write the balanced chemical reaction:

   $$4\text{Al} + 3\text{O}_2 \rightarrow 2\text{Al}_2\text{O}_3$$

2. Molar mass of Al = 27 g/mol.
   For 27 g of Al, moles of Al = $\frac{27}{27} = 1$ mol.

3. According to the equation, 4 moles of Al require 3 moles of $\text{O}_2$.
   So, 1 mole of Al requires $\frac{3}{4}$ mole of $\text{O}_2$.

4. Molar mass of $\text{O}_2 = 32$ g/mol.
   Mass of $\frac{3}{4}$ mole of $\text{O}_2 = \frac{3}{4} \times 32 = 24$ g.