Answer: The correct answer is option B i.e., 2.78 mol
Explanation:
Aluminium reacts with iodine to form Aluminium iodide

From the equation, it is clear that 3 moles of iodine reacts with 2 moles of Aluminium to form Aluminium iodide
We know
For 2 moles of Aluminium, 
3 moles of Iodine reacts with 54 g of Aluminium
? moles of iodine react with 50 g of Aluminium
Answer:
4.52 mol
Explanation:
We do grams/Molar Mass to find the number of moles. The grams are given but the molar mass, you have to add all masses of the elements up by refering to a periodic table, and you should get that the compound has a mass of 158.168. Do 715.11 dived by that and you get the answer above.
The correct answer is ...... The product of Ka and Kb equals the auto-dissociation constant for water. I know its right for sure!