2. Air, natural water and liquor are three different substances, but they all belong to (mixture). This kind of substance, from a macro point of view, is composed of (pure substance).
There is some connection between the following substances, please analyze them carefully, find the law, and give another similar example respectively. A. nitrogen, sulfur, mercury, (gold) B. sodium chloride, water, carbon dioxide, (carbon monoxide)
4. Sucrose is an important sweetener that we often come into contact with in our daily life. Please take part in the inquiry activities of the chemistry activity group and answer relevant questions.
(1) 【 Question 】 What elements are sucrose composed of?
(2) [Guess] Xiaohua suggested that sucrose would turn (black) if it was heated in the pot for too long. Therefore, it is speculated that sucrose contains carbon and perhaps other elements.
(3) [Collection of data] ① Sucrose is a compound containing carbon, so it belongs to (pure substance) (fill in "pure substance" or "mixture"). Sucrose can burn and decompose when heated, which belongs to the (chemical) (fill in "physical" or "chemical") nature of sucrose. ② The essence of chemical reaction is (generating new substances), so before and after chemical reaction, the types of elements are (constant) (fill in "constant", "increase" or "decrease").
(4) Students in the [Design Experiment] group designed two experimental schemes:
(1) ignite sucrose in the air. It is found that sucrose is not easy to burn when it is ignited alone, but it is easy to burn when a small amount of soot is mixed in sucrose. It can be seen that cigarette ash may play a role in the combustion reaction of sucrose. When sucrose burns, the flame is covered with a small dry beaker with water droplets on the inner wall of the beaker. Add lime water to the small beaker to make it turbid.
(2) put sucrose into a closed container to increase the heat. It was found that sucrose gradually turned black and water droplets were produced on the inner wall of the container.
(5) 【 Conclusion 】 The reactions in the above two schemes are expressed by literal expressions: ① (sucrose+oxygen → carbon dioxide+water); ② (sucrose → water+carbon). Sucrose consists of three elements (carbon), (hydrogen) and (oxygen).
(6) [Reflection and Evaluation] Which of the two experimental schemes would you choose? Why?
The first and second substances that may be blackened are not carbon.
5. Read the following materials: The chemical name of quicklime is calcium oxide. (1) quicklime mixed with water into lime slurry, used to wipe the room walls. (2) the lime slurry constantly absorb carbon dioxide in the air, gradually become hard, become calcium carbonate. At the same time, the newly painted wall gradually became damp, as if the whole body of the lime wall was sweating. (3) "In a room with newly painted lime walls, coals are often lit. Do you want to dry the room? No, it's because there is only 0.03% (volume fraction) carbon dioxide in the air. Burning a charcoal fire is to increase the content of indoor carbon dioxide and speed up the hardening of lime slurry. " Please use chemical equations to express the three chemical reaction principles in the information according to the relevant information and knowledge of the material.
①_ _ _ _ _ _ _ _ _ _ CaO+H2O = Ca(OH)2 _ _ _ _ _ _ _ _ _ _ .
②_ _ _ _ _ Ca(OH)2+CO2 = CaCO3↓+H2O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ .
③_ _ _ _ _ _ _ _ _ _ C+O2 =△= CO2 _ _ _ _ _ _ _ _ _ _ .
6. The experiment in the laboratory needs to produce a small amount of acetylene gas. Xiao Ting explored the method of producing acetylene. Please participate in her exploration process and answer relevant questions.
Xiao Ting first consulted relevant information and obtained the following information:
Acetylene (C2H2) is a colorless, odorless and odorless gas, lighter than air, slightly soluble in water and easy to burn.
(2) (a) Natural gas can react in electric furnace at high temperature to generate acetylene: 2ch 4 C2 H2+3 H2 at high temperature.
(b) solid calcium carbide (CaC2) reacts with water to generate acetylene: cac2+2h2o = ca (oh) 2+c2h2 =
(1) The laboratory should choose the reaction that produces acetylene gas as (b) (fill in "a" or "b"), and the reason for choosing this reaction is (convenient, it is difficult for the laboratory to reach high temperature, and there is no electric furnace).
(2) The laboratory has two sets of gas generating devices.
(1) indicates the name of the instrument in the equipment:
a.( ) ; b .()； c .
(2) choose the device to produce acetylene is () (fill in "a" or "b"). The reason why you choose this device is (), which can also be used to make directional downward exhaust in the laboratory), and the reason why you choose this method is (ethylene is less dense than air and slightly soluble in water).
Without a picture, I can't write a little space.