Answer: The 
value is 0.664
Explanation:
Distance travelled by solvent front = (7.7-1.45)cm = 6.25 cm
Distance travelled by unknown = (5.6-1.45) cm = 4.15 cm
The retention factor or the value is defined as the ratio of distance traveled by the unknown to the distance traveled by the solvent front.
Thus the value is 0.664
Sodium is very reactive but it’s a metal, and the problem asks specifically for a non-metal.
Silicone is technically reactive, but not super reactive.
Argon is a nonmetal, however it is an inert gas. It doesn’t react with anything.
We’re left with Chlorine, which is a non-metal in group 7, a highly reactive group, on the periodic table.
You should read up on Proust's law, better known as the Law of Definite Proportions. This is a chemical law that defines your question more generally, on why the ratio of elements and ions are always fixed.
Basically, this compound Magnesium(II) Chloride is MgCl2 because it has the same number of protons, neutrons, and electrons all the way. This defines the properties of the compound or atom.
Explanation:
Reaction equation for the given chemical reaction is as follows.
Equation for reaction quotient is as follows.
Q = 
= 
= 0.256
As, Q > K (= 0.12)
The effect on the partial pressure of 
as equilibrium is achieved by using Q, is as follows.
- This means that there are too much products.
- Equilibrium will shift to the left towards reactants.
- More is formed.
- Partial pressure of increases.
