pure water has a ph of 7. pure water _______.; when using ph paper, the ph of a solution can be determined by looking at the _______ of the paper.; litmus paper can be used to determine the _______ of a substance.; is baking soda an acid or base; in a chemical reaction, the products are; blood maintains a ________ ph.; which of the following molecular models represents an element?; the element oxygen, represented by the symbol o, is classified as