Wow, now this one is a hard one, took me quite a while to figure it out but here it is:

The abundances of the two isotopes is:
Antimony-121 = 57.2%
Antimony-123 = 42.8%
Answer:
Erosion/Weathering
Explanation:
Because the rock is exposed to the ocean, the constant push and pull of the water against the rock erodes the material away and moves it elsewhere. The wind likely aided in this process as well. This caused the big gap in the center of the rock.
Answer:
The boiling point of sample X and sample Y are exactly the same.
Explanation:
The difference between sample X and sample Y is that they occupy different volumes. However, they both contain pure water. Remember that pure water has uniform composition irrespective of its volume.
Volume does not affect the boiling point as long as the volume is small enough not to give rise to significant pressure changes in the liquid.
The boiling point of a liquid is the temperature at which the pressure exerted by the surroundings upon a liquid is equaled by the pressure exerted by the vapour of the liquid; under this condition, addition of heat results in the transformation of the liquid into its vapour without raising the temperature.
It can be clearly seen from the above that the volume of a solution of pure water does not affect its boiling point hence sample X and sample Y will have the same boiling point.
Answer:
b)5l x 10kg c)10kg + 9l (Not sure for the last 1)