How many O's are in Al2(SO4)3 ?

Why is an elements atomic mass not listed as a whole number on the periodic table

The boiling point of liquids is very high what does it indicate

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?