A solution has a [H+] of 0.20 M. Find the pH of this solution.

The pH of this solution : 0.699

pH is the degree of acidity of a solution that depends on the concentration of H⁺ ions. The greater the value the more acidic the solution and the smaller the pH.  

pH = - log [H⁺]  

So that the two quantities between pH and [H⁺] are inversely proportional because they are associated with negative values.  

A solution whose value is different by n has a difference in the concentration of H⁺ ion of 10ⁿ.  

A solution has a [H+] of 0.20 M, so [H⁺]=0.2

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.