Answer;
D, Xe (g)
Solution and explanation;
If 2g has a volume of 340ml.
Density is 1000/340*2 = 5.88g/litre.
-This rules out the two solids, choices 2) &3)
If 1 litre has mass 5.88g,
then 22.4 liters (volume at STP) has mass 5.88*22.4 = 131.8g/mol
molar mass Br2 = 80*2 = 160g/mol NO
molar mass Xe = 131.3g/mol = YES.
Answer is Xe