Answer:
2.1 M is the molarity of the HCl solution.
Explanation:

Molarity of HCl solution = 
Volume of HCl solution = 
Ionizable hydrogen ions in HCl = 
Molarity of NaOH solution = 
Volume of NaOH solution = 
Ionizable hydroxide ions in NaOH = 
(neutralization )


2.1 M is the molarity of the HCl solution.
Answer: for 3. I would say it means that the amplitude is greater because if a sound is louder that means the amplitude is larger, same with the light.So that would mean the softer the sound the smaller the amplitude same with the dim of the light so for 4. It would be the amplitude is smaller. Hope this helps! :) ( if you have any questions feel free to ask)
The Mr is the mass numbers of each element added up so…. Fe = 56, O=16, H=1 … now add these up with the number of each element -> there’s 1 Fe, and 3 Os and 3 Hs as they are in brackets with a 3 outside-> (56+16+16+16+1+1+1=107) … your answer is 107