If there is no mass # and n # how do you find the mass # and n #

0.09 moles of sodium sulfate in 12 ml of solution

Which of the following would be an accurate picture of the earth during the summer time of the northern hemisphere?

Oil rich countries in the middle east cover about 4% of earths total land area but prossess about 48% of the worlds known oil reserves what is the main reason for high concentration of reserves in this part of the world