Answer:
It would be 5.8 times 10^9cm
pH is a symbolic representation of:

and for water we now that:

that means the text give us the information to calculate the concentration of protons and therefore the concentration of ions OH-:

therefore the concentration of OH- can be calculated:

but they are not asking about the concetration of OH- they ask about concentration of Ba(OH)2 and for that we need to know the disolution stechiometry

Whic mean the concentration of Ba(OH)2 is half the concentration of OH-:
200 moles of nitric acid.
Explanation:
We have the following chemical equation:
3 NO₂ + H₂O → 2 HNO₃+ NO
Taking in account the chemical equation, we devise the following reasoning:
if 3 moles of nitric dioxide (NO₂) produce 2 moles of nitric acid (HNO₃)
then 300 moles of nitric dioxide (NO₂) produce X moles of nitric acid (HNO₃)
X = (300 × 2) / 3 = 200 moles of nitric acid.
Learn more about:
number of moles
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Answer:
Scientific ideas are changed when better ones are found.
Explanation: