(1) The acidity and alkalinity of food and the acidity and alkalinity of solution in chemistry are different concepts. Refers to the acidity or alkalinity of food, which is classified according to the nature of the final products of food metabolism in the body. Protein, for example, is digested and absorbed in the body and eventually oxidized into acid. This kind of food is physiologically called acidic food, and is customarily called acidic food. Some vegetables and fruits contain more potassium and sodium. After metabolism in the human body, alkaline substances are generated, making body fluids weakly alkaline. These foods are customarily called alkaline foods, and they are either acidic in taste or acidic. Although citric acid is very acidic, it generates carbon dioxide and water after oxidation in the body, leaving alkaline potassium salt, so it belongs to alkaline food.
So, the answer is: acidic; Alkalinity;
(2) Vitamin C contains six C's, eight H's and six O's, and its molecular formula is C6H8O6. The functional groups contained in the molecule include hydroxyl groups, ester groups and carbon-carbon double bonds, among which the functional groups without oxygen are carbon-carbon double bonds. Mashing the fruit, dissolving it in water, and filtering to obtain filtrate containing vitamin C. It shows that vitamin C is soluble in water, and ferric chloride turns red when it meets KSCN solution. After adding the filtrate containing vitamin C, it was found that the red color disappeared after shaking.
So the answer is: C6H8O6；; Carbon-carbon double bond; reducing power