The answer would be a tenfold increase<span>
The pH scale is calculated based on the concentration of H+ ion in the solution. The formula is using log10, so to decrease 1 unit from the scale it will be 10^1= 10 fold of increase. For 2 </span>unit, you will need 10^2= 100 fold of increase.
NaOH + HNO₃ --------> NaNO₃ + H₂O
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NaNO₃ - sodium nitrate
