What is the difference between 0.50 mol HCl and 0.50 M HCl?

100mg magnesium reacts with 20ml of 1.0m hcl

Which substance has non polar covalent bonds

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 ?