Answer:
b) Silicon and oxygen
Explanation:
A compound is a pure substance that contains two or more atoms chemically joined together. Sand is regarded as a 'compound' because it is made up of two or more atoms that are chemically bonded to one another.
Sand is said to predominantly contain silica, which has a chemical formula of SiO2. Hence, sand can be said to be a compound containing one atom of silicon (Si) and two atoms of oxygen (O2).
Answer is: CuCl₂·2H₂O is limiting reactant.
Chemical reaction: 3CuCl₂·2H₂O + 2Al → 3Cu + 2AlCl₃ + 6H₂<span>O.
</span>m(Al) = 0,5 g.
m(CuCl₂·2H₂O) = 3,5 g.
n(CuCl₂·2H₂O) = m(CuCl₂·2H₂O) ÷ M(CuCl₂·2H₂O).
n(CuCl₂·2H₂O) = 3,5 g ÷ 170,5 g/mol.
n(CuCl₂·2H₂O) = 0,0205 mol.
n(Al) = 0,5 g ÷ 27 g/mol.
n(Al) = 0,0185 mol.
From chemical reaction: n(Al) : n(CuCl₂·2H₂O) = 2 : 3.
0,0185 mol : n(CuCl₂·2H₂O) = 2 : 3.
n(CuCl₂·2H₂O) = 0,02755 mol; there is no enough n(CuCl₂·2H₂O).
