Helium has a density of 1.79 x 10-4 g/ml at standard temperature and pressure. a balloon has a volume of 6.3 liters. calculate the mass of helium that it would take to fill the balloon. be sure to follow significant figure rules when calculating the answer.

At a temperature of 393 k, the temperature of a sample of nitrogen is 1.07 atm what will the pressure be at a temperature of 478 k

This chart lists four kinds of polymers and their sources. what can be known about all four polymers, despite their differences? they come from living things. they share ionic carbon bonds. they are at least 100 monomers long. they are made of repeating subunits.

Suppose you mix one mole of sulfuric acid (h2so4) with 1 mole of sodium hydroxide(naoh). why does the ph of the solution remain below 7? ( explain so i can get better understanding! )