Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g)
(since the molar mass of Mg is not given, assuming that it's mola mass is 24gmol¯1)
1st find the moles of Mg using the equation n=m/M where
n - moles
m - mass
M - molar mass
Therefore :

n = 0.39375mol
n = 0.39mol
Then using the equation n=V/Vm where;
n = mol
V = volume
Vm = molar volume
Find the volume.
n = V/Vm
(n =0.39mol , Vm = 22.4dm³mol¯¹)
V = 0.39mol×22.4dm³mol¯¹
V = 8.736dm³
A. Kinetic energy of molecules
Metals, for example Cesium and Francium
I believe it's better for it to be more abundant because it's better to have more then less. Take water as an example. Water is an important factor to our survival and if we didn't have enough of that we would be in trouble. Or if we needed food but there wasn't enough more people would be dying from starvation. It's better to have a little more than a little less.