Answer:
Normality N = 0.2 N
Explanation:
Normality is the number of gram of equivalent of solute divided of volume of solution, where the number of gram of equivalent of solute is weight of the solute divided by the equivalent weight.
Normality is represented by N.
Mathematically, we have :

Given that:
number of gram of equivalent of solute = 90 milliequivalents 90 × 10⁻³ equivalent
volume of solution (HCl) = 450 mL 450 × 10⁻³ L

Normality N = 0.2 N
It would be Magnesium = 1 atom, Oxygen = 2 atoms, Hydrogen = 2 atoms. It has 5 atoms total. There is 1 magnesium and you multiply each element by the the 2 outside the parenthesis to get 2 oxygen and 2 hydrogen.
The balanced equation for reaction of solid cesium with liquid water
= 2Cs + 2H2O → 2CsOH + H2
cesium react with liquid water to produce cesium hydroxide and hydrogen gas
that is 2 moles of Cs react 2 moles of H2O to form 2 moles CsOH and 1 of hydrogen gas
C. Weak acids partially ionize