Answer : The mass of helium gas in the balloon is, 1.23 grams.
Explanation : Given,
Volume of helium gas = 6.9 L
First we have to calculate moles of helium gas at STP.
As we know that, 1 mole of substance occupy 22.4 L volume of gas.
As, 22.4 L volume of helium gas present in 1 mole of helium
So, 6.9 L volume of helium gas present in
of helium
Now we have to calculate the mass of helium gas.

Molar mass of He gas = 4 g/mol

Thus, the mass of helium gas in the balloon is, 1.23 grams.
The location that volcanoes are consistently found in the world is near the Ring of Fire so the answer would basically be "Continent-ocean boundaries".
I would say vapor pressure, but I could be wrong. Good luck ^^
<span>a. a chemical combination of two or more different materials.
For example: </span>For example, air is a mixture of gases, containing N, O, Ar, CO2
The answer is deformation of rocks. hope it helps :)