Ionic compounds are compounds that are formed together by a cation and an anion. A cation is an ion with a positive charge. For example, Na+ and Ca2+. An ion has a negative charge, like Cl- and OH-. There is a greater chance of forming an ionic compound when they have a great difference in electronegativity, the ability to attract electrons toward itself. In the periodic table, elements that are opposite to each other, more likely found in opposite sides, would be more apt to form an ionic compound. Example would be NaCl and CaCl2 or Ca(OH)2.
You just need to convert it into moles per Liter (mol/L).
0.0815mol / 0.550L = 0.148mol/L
Depends on where the object is. On earth, moon , or somewhere without any other mass (theoretically). I think you mean how much does weigh on earth. So, the average gravitational acceleration on earth is : 9.83 m/s^2 To find out how much an object weighs, this is the formula : G=m.g where m is mass of the object g is the gravitational acceleration and G is weight. So, G = 10.9,83 = 98,3 N is the answer.