Answer:
Mass = 28.08
Explanation:
Given data:
Mass of Al₂O₃ = 21.8 g
Mass of water = 9.7 g
Mass of Al(OH)₃ = ?
Solution:
Chemical equation:
2Al(OH)₃ → Al₂O₃ + 3H₂O
Number of moles of water:
Number of moles = mass/molar mass
Number of moles = 9.7 g/ 18 g/mol
Number of moles = 0.54 mol
Number of moles of Al₂O₃:
Number of moles = mass/molar mass
Number of moles = 21.8 g/ 101.96 g/mol
Number of moles = 0.21 mol
Now we will compare the moles of Al(OH)₃ with Al₂O₃ and H₂O.
Al₂O₃ : Al(OH)₃
1 : 2
0.21 : 2×0.21 = 0.42 mol
H₂O : Al(OH)₃
3 ; 2
0.54 : 2/3×0.54 = 0.36 mol
Mass of Al(OH)₃:
Mass = number of moles × molar mass
Mass = 0.36 mol × 78 g/mol
Mass = 28.08 g
