The answer is 10 times higher in the cytoplasm than in the mitochondrial matrix
pH is usually calculated by the negative log of the H+ ions in a solution. The H+ ions are calculated in mols/Liter; Therefore a solute with a higher concentration of hydrogen ions has a lower pH. The difference between one pH to the next is 10 times fold the number of H+ ions.
[H+]= mol/L.
pH=−log[H+]