a spherical balloon with a diameter of 6 m is filled with helium at 20 degree c and 200 kpa. determine the mole number.

Did the universe cool off or get hotter as it expanded after the 'big bang"?

Which of the following always exist between two objects having mass ● elastic force ● contact force ●gravitational force ●magnetic force

28. the new systematic nomenclature was so ( that many chemists preferred to ( the older trivial names that were at least shorter. at least, that is the ostensible reason. actually, tradition seems to carry more weight than ( with some scientists.