Protons can't change in stable elements so its means that is Barium
Shape
A gas is shapeless all other things being equal. It will, if put in a container, occupy every part of the container.
A liquid could also be thought of shapeless. If put in a container, it need not occupy the entire container. It will occupy as much as its calculated volume will permit it to occupy.
A solid will only occupy its original shape.
Volume
A gas will occupy whatever container it is put in within limits. You cannot put a 72 mols of gas in a mm^3 container without some amazing ability to apply a lot of pressure.
A liquid will occupy a volume determined by its density and mass. In general liquids cannot be compressed.
Whatever volume a solid has to start with, it will retain that volume all other things being equal.
This is actually very hard to describe.
MH₂ = 2×mH = 2×1g = 2 g/mol
<span>Platinum is solid at room temperature. SInce the catalyst is solid while the medium involves gases, this catalyst is characterized as heterogenous. Because they are different states of matter, they can be easily separated through physical means. So, the answer is B.</span>
