The concentration of h ions inside the mitochondrial matrix is lower than it is in the cytosol or the mitochondrial intermembrane space. what would be the immediate effect of a membrane-permeable compound that carries and releases protons

The protons will  be carried by the compound from the cytosol into the inter-membrane space and the mitochondrial matrix. Once the concentration of protons is the same between the cytosol and the mitochondrial matrix, the movement of protons will cease. This is because ions move across a membrane along the concentration gradient.  

A solution with higher pH levels is more basic. That is because 7 is neutral. Higher than 7 is basic, and lower than 7 is acidic.

Final basic