Why is MgOH is much more effective antacid than calcium or BaOH

In apex! a liquid heated beyond a certain temperature becomes

An atom of which element reacts with an atom of hydrogen to form a bond with the greatest degree of polarity ?

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 ?