Answer:

Explanation:
The limiting reactant is the reactant that gives the smaller amount of product.
Assemble all the data in one place, with molar masses above the formulas and masses below them.
M_r: 39.10 80.41 2.016
2K + 2HBr ⟶ 2KBr + H₂
m/g: 5.5 4.04
a) Limiting reactant
(i) Calculate the moles of each reactant

(ii) Calculate the moles of H₂ we can obtain from each reactant.
From K:
The molar ratio of H₂:K is 1:2.

From HBr:
The molar ratio of H₂:HBr is 3:2.

(iii) Identify the limiting reactant
HBr is the limiting reactant because it gives the smaller amount of NH₃.
b) Excess reactant
The excess reactant is K.
c) Mass of H₂

A density of the substance is an intrinsic property. Each substance has its own value of density, and it is constant. Since density is equal to mass over volume, a graph of mass vs volume would have a constant slope equal to density. So, it will be a linear graph. The mass is in the y-axis, and the volume is on the x-axis. Locate V = 16 mL on the x-axis, project it upwards until it intersects with the linear graph, then, move towards the left to determine the corresponding y-value, represented by the mass.
You spelled calendar incorrectly, the correct spelling is the one I previously wrote...Calendar
4.88x10^20 H2O2 molecules