Aluminum forms a layer of aluminum oxide when exposed to air which protects the

Question

Aluminum forms a layer of aluminum oxide when exposed to air which protects the bulk metal from further corrosion. 4AI(s) + 3O_2(g) rightarrow 2AI_2 O_2(s) Using the thermodynamic data provided below, calculate Delta S degree for this reaction. a. 182.3 J/K-mol b. 131.5 J/K-mol c. -182.3 J/K-mol d. -626.2 J/K-mol e. -802.9 J/K-mol Aluminum is an active metal, but does not corrode as iron does because a. AI does not react with O_2. b. A protective layer of AI_2 O_3 forms on the metal surface. c. AI is harder to oxidize than is Fe. d. The enthalpy of formation of aluminum oxide is negative. c. Aluminum has a high tensile strength. Which of the following yields a buffer solution when equal volumes of the two solutions are mixed? a. 0.10 M NH_3 and 0.10 M HCI b. 0.10 M NH_4^+ and 0.10 M KOH c. 0.20 M NH_3 and 0.10 M KOH d. 0.20 M NH_3 and 0.10 M HCI e. 0.20 M NH_4^+ and 0.10M HCI

Explanation / Answer

1) 4Al + 3O2 ----------> 2Al2O3

delta S = 2 SoAl2O3 -(  4 SoAl + 3Soo2)

delta S =2 x 50.99 - ( 4 x 28.3 + 3 x 205 )

delta S = -626.22 J/Kmol

2) ans is B

When aluminium reacts with oxygen it provides a thin protective layer known as aluminium oxide (Al2O3),Which prevents from corrosion

3) ans is D

20M NH3 and 10M HCl (NH3 is a base)

HCl react only 10 mole of NH3 to form NH4+

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