What is the mass of 2.4 × 1023 molecules of no2? 12 g 1.2 × 102 g 75 g 1.1 × 1023 g 18 g

As we know, 
                    1 mole of any substance contains 6.022 × 10²³ particles. And 1 mole of NO₂ (equal to 46 g) contains 6.022 × 10²³ Molecules. Hence,

                           6.022 × 10²³ Molecules of NO₂  =  46 g
So, 
                               2.4 × 10²³ Molecules of NO₂  =  X g

Solving for X,
                          X  =  (2.4 × 10²³ Molecules × 46 g) ÷ 6.022 × 10²³ Molecules

                          X  =  18.33 g

True, the standard unit for volume is liters which can be represented by either a lower case "l" or a capital "l"