Answer: the pH is 11.78
Explanation:Please see attachment for explanation
The equation for energy of a photon is E=hv where v equals frequency and h equals the Planck constant (6.626X10^-34). So since you've been given frequency you can just plug in frequency to find the total energy in joules.
E=(3.55X10^17)(6.626X10^-34)
E=2.35223X10^-16
Not sure how many significant figures you needed. Hope this helped.
FeBr₃ ⇒ limiting reactant
mol NaBr = 1.428
<h3>Further explanation</h3>
Reaction
2FeBr₃ + 3Na₂S → Fe₂S₃ + 6NaBr
Limiting reactant⇒ smaller ratio (mol divide by coefficient reaction)
211 g of Iron (III) bromide(MW=295,56 g/mol), so mol FeBr₃ :

186 g of Sodium sulfide(MW=78,0452 g/mol), so mol Na₂S :

Coefficient ratio from the equation FeBr₃ : Na₂S = 2 : 3, so mol ratio :

So FeBr₃ as a limiting reactant(smaller ratio)
mol NaBr based on limiting reactant (FeBr₃) :

The concentration of the hydrogen ions from molarity can be given with the number of hydrogen atoms in the molecular formula.
<h3>What is molarity?</h3>
Molarity is given as the moles of the solute present in a liters of solution. The compound with the number of hydrogen atoms in the molecular formula with degradation possesses the equivalent concentration of the hydrogen ions.
The compound with molecular formula AH having molarity 2, will produce 2M of hydrogen ions.
Learn more about molarity, here:
brainly.com/question/2817451
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