The concentration of fluoride, lead, nitrate and iron in a water sample from an underground lake was found to be 1000 ppb, 40 ppb, 100 ppm and 0.2 ppm, respectively. This water is unsuitable for drinking due to high concentration of :

Which of the following statements about low density polythene is FALSE ?

Two closed bulbs of equal volume $$(V)$$ containing an ideal gas initially at pressure $${p_i}$$ and temperature $${T_1}$$ are connected through a narrow tube of negligible volume as shown in the figure below. The temperature of one of the bulbs is then raised to $${T_2}.$$ The final pressure $${p_f}$$ is :

The absolute configuration of



is :