Mostly explaining isotopes?

Agas has a volume of 0.7 l at 300 mmhg. what would be the new volume at 900 mmhg

The reaction q+r2=r2q is found to be first order in r2 and

You are making a solution of calcium chloride dissolved in water. you add solid, stir, and it dissolves. you add just a spatula tip full, stir, and the solid does not dissolve. how could you describe the solutions before and after adding the spatula tip amount