For plato users
the answer is a. O2(l) O2(g)
hope this helps!
Vanadium (V)
Vanadium is the only one in the 4th period here so
So to balance an equation, you need to get the same amount of each type of element on either side of the --> . So you pretty much are given the subscripts in the equations and you need to add coefficients (just normal numbers) in front of any formula that needs it, keeping anything balance.

turns into

These coefficient numbers are the molar ratios, so 2 moles of KCl3 for every 3 moles of O2 so 1. 3:2
Then you can use these ratios of find out how many moles of one thing are needed if you are given the amount of another.

and use cross multiplication to solve for whatever you don't know
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Answer:
[H+] = 1.74 x 10⁻⁵
Explanation:
By definition pH = -log [H+]
Therefore, given the pH, all we have to do is solve algebraically for [H+] :
[H+] = antilog ( -pH ) = 10^-4.76 = 1.74 x 10⁻⁵
That would be 3.621471•10^3