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Those years of pits our desiccant test questions
- Mar 20, 2016 -

(2010•Zhanjiang college entrance examination questions) Foods are prone to deterioration after moisture absorption and oxygen absorption. In order to extend the shelf life of foods, a small packet of desiccant is usually added to the package. A chemical interest group has reviewed the information and found that there are two main food desiccants. Species: a desiccant with lime as the main component (referred to as Class A, the same below); the other is desiccant with silica gel as the main component (referred to as Class B, the same below). Please answer the following questions:


(1) The small paper bag containing the desiccant of class A is opened and exposed to the humid air, and the paper bag is heated. The chemical equation of the reaction is CaO+H2O=Ca(OH)2. (The reaction of calcium oxide and water can be generated. Calcium hydroxide, so fill: CaO+H2O=Ca(OH)2.)

(2) The main component of silica gel in class B desiccant is (SiO2•nH2O) SiO2 is (oxide), (2) silica is a compound composed of silicon and oxygen, which belongs to oxide. Object.

(3) In the inspection data, the group also discovered a new type of food desiccant: foamed iron powder (iron powder wrapped in foam). When it is exposed to moist air, it quickly turns into rust (mainly The composition is Fe2O3•nH2O), and there is a fever phenomenon, indicating that in addition to the formation of new substances, the chemical reaction is accompanied by heat changes. Compared with the class A desiccant, the foamed iron powder can be used as an oxygen absorber in addition to the desiccant. (deoxidizer)



2014 National Higher Education Enrollment National Unified Examination (Sichuan Volume)

1. Chemistry is closely related to life. The following statement is incorrect.

A. Ethylene can be used as a ripening agent for fruits B. Silica gel can be used as a desiccant for bagged foods C. Formalin can be used as a preservative for foods D. Aluminium hydroxide can be used as a neutralizing agent for gastric acid


Answer analysis:

Analysis of test questions: A, ethylene is a plant growth regulator, can be used as a ripening agent for fruits, A is correct; B, porous silica gel, strong ability to absorb water, can be used as a desiccant for bagged food, B correct; C, Fu Is the aqueous solution of formaldehyde, formaldehyde is toxic, can not be used as a preservative for food, C is not correct; D, aluminum hydroxide is an amphoteric hydroxide that can react with acid, can be used as a neutralizer for gastric acid, D is correct, the answer is C.



8. The following statement is incorrect.

A. The color changing silica gel desiccant contains CoCl2, and when the desiccant is blue, it means no water absorption and drying function.


B. In the preparation of nitrobenzene, the thermometer was inserted into the water bath, but the mercury ball could not be in contact with the bottom of the beaker and the wall of the beaker.


C. In the neutralization titration experiment, the volumetric flask and the conical flask can be used after washing with distilled water. After the burette and pipette are washed with distilled water, they must be dried or rinsed before use.


D. Removing a small amount of SO2 mixed in the dry CO2, the mixed gas can be sequentially passed through a gas-washing bottle containing an acidic KMnO4 solution and concentrated sulfuric acid.


The bag length is 25CM, the width is 35CM, the bag air permeability is 8ML/square/day, and the product storage period is 1.5 years. How many types of deoxidizers should be selected?


Answer:

[ Oxygen content in the bag: ( 25 * 35 * 1 * 0.21) + bag oxygen permeability: (0.25 * 0.35 * 2 * 8 * 548 * 0.21)] / 3 = 115 select 100CC


Do you know?

In dry air, the volume of oxygen is about 21%.


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