What is earths surface made of?

What is the mass of 8 moles of sodium atoms

Sodium sulfate dissolves as follows: na2so4(s) → 2na+(aq) + so42- (aq). how many moles of na2so4 are required to make 1.0 l of solution in which the na concentration is 0.10 m?

The identities of substances are the same before and after which type of change