Answer:
8.66 g of Al₂O₃ will be produced
Explanation:
4Al (s) + 3O₂ (g) → 2Al₂O₃ (s)
This is the reaction.
Problem statement says, that the O₂ is in excess, so the limiting reactant is the Al. Let's determine the moles we used.
4.6 g / 26.98 g/mol = 0.170 moles
Ratio is 4:2.
4 moles of aluminum can produce 2 moles of Al₂O₃
0.170 moles of Al, may produce (0.170 .2)/ 4 = 0.085 moles
Let's convert the moles of Al₂O₃ to mass.
0.085 mol . 101.96 g/mol = 8.66 g
Answer: a) Temperature of 
b) 
c) dehydrating agent
Explanation:
Ethanol is heated with an excess of concentrated sulfuric acid at a temperature of 170°C to produce ethene.
The balanced chemical reaction is:

Here concentrated sulfuric acid removes a water molecule from ethanol and thus acts as a dehydrating agent.
Ksp=3.45×10⁻¹¹
CaF₂(s) ⇄ Ca²⁺(aq) + 2F⁻(aq)
Ksp=[Ca²⁺][F⁻]²
[Ca²⁺]=C(CaF₂)
[F⁻]=2C(CaF₂)
Ksp=4{C(CaF₂)}³
C(CaF₂)=∛(Ksp/4)
C(CaF₂)=∛(3.45×10⁻¹¹/4)=2.05×10⁻⁴ mol/L
2.05×10⁻⁴ M