Which layer of the atmosphere contains almost 80% of the atmospheres total mass

Concerning the 10.0 ml of 0.50 m nacl to 100 ml of solution: when a solution is diluted, does it change the number of moles dissolved?

For the following, determine the type of reaction and then give products.

Given the following equation: 2a1 + 3mgcl2 --> 2alcl3 + 3mg how many moles of aluminum chloride are produced from 2.5 moles of magnesium chloride?