Currently doing a quiz, who ever can help me first gets brainliest! Please do help ita for grades

Which statement is true about ionic compounds?

How would the number of moles (n) of o2 change if the atmospheric pressure doubled but all other variables stayed the same

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 ?