A 1.68L sample of krypton gas contains 0.330mol of krypton. How many ADDITIONAL moles of krypton must be added to this sample to expand its volume to...

A 1.68L sample of krypton gas contains 0.330mol of krypton. How many ADDITIONAL moles of krypton must be added to this sample to expand its volume to 19.9L? Assume temperature and pressure remain constant.

A weather balloon is inflated with helium (He) gas to a volume of 1.61 L at an ambient temperature of 23.5 °C and pressure of 1.15 atm. 

Once the balloon has reached a higher altitude, its volume has changed to 2.47 L and the temperature is now 15.5 °C.

What is the ambient (atmospheric) pressure at this altitude (in atm)? Express your answer to two significant figures. Assume the helium is an ideal gas and there are no leaks in the balloon.