1.an acid is a substance that has a ph value that is lower than 7. a base is a substance that has a ph that is greater than 7. citric acid commonly present in sour foods. which one of these might be the ph of a citric acid solution? ph=3.2 ph=7.0 ph=10.3 ph=14.0 2.which mixture is homogenous? salt stirred together with sugar sugar dissolved in water water droplets scattered in the air to form fog dirt suspended in water 3. which mixture is heterogeneous salt dissolved in water air metal ally tossed salad