From the experiment to learn chemistry
A chemical experiment safety
1, (1) to do the experiment of toxic gases, should be carried out in the ventilation kitchen, and pay attention to the tail gas for appropriate treatment (absorption or ignition, etc.). When conducting experiments on flammable and explosive gases, attention should be paid to the purity test, and the exhaust gas should be burned off or treated appropriately.
(2) It is advisable to seek medical attention for burns.
(3) If concentrated acid is spilled on the lab bench, neutralize it with Na2CO3 (or NaHCO3) and then rinse it off with water. If the acid gets on your skin, wipe it off with a dry cloth and then rinse it off with water. If you get acid in your eyes, rinse them with dilute NaHCO3 solution, then call a doctor.
(4) Concentrated alkali spilled on the experimental bench, first neutralized with dilute acetic acid, and then rinsed with water. If the alkali is stained on the skin, rinse with plenty of water and then apply boric acid solution. If you splash alkali in your eyes, wash them with water and then use boric acid solution to rinse them.
(5) Sodium, phosphorus and other misfires should be covered with sand.
(6) alcohol and other flammable organic small fire, should be quickly covered with a wet rag.
II. Separation and purification of mixtures
Separation and purification methods Separation of substances Matters to be noted Application examples
Filtration for solid-liquid mixture of separation of a paste, two low, three rely on the purification of such as crude salt
Distillation Purification or separation of liquid mixtures with different boiling points Prevent the liquid from boiling violently, the location of the thermometer's mercury bulb, such as the condensate tube of petroleum in the distillation of the flow of water such as the oil distillation of petroleum
Extraction of solutes in immiscible solvents with different solubility, with a solvent to extract the solute from the solution it consists of with another solvent The selection of the extractant should meet the following requirements: and the solvent is immiscible with each other in the original solution; solubility of solutes should be much greater than the original solvent extract bromine, iodine in bromine water with carbon tetrachloride
Separation of the separation of the liquid that is not mutually soluble. Separation of mutually insoluble liquids Open the upper end of the piston or make the groove on the piston and the water hole on the funnel, so that the air inside and outside the funnel is connected. Open the piston, so that the lower liquid slowly flow out, close the piston in time, the upper liquid from the upper end of the pouring such as carbon tetrachloride to extract bromine, iodine in the bromine water and then liquid separation
Evaporation and crystallization used to separate and purify the mixture of several soluble solids Heating evaporation dish to make the solution evaporate, the solution should be constantly stirred with a glass rod; when more solids in the dish, that is, stop the heating Separation of NaCl and KNO3 mixture
Separation of the liquid from a mixture of insoluble liquids
Separate the liquid from a mixture of insoluble liquids
Three, ion test
Ion added reagent phenomenon Ionic equation
Cl- AgNO3, dilute HNO3 produce white precipitate Cl- + Ag + = AgCl↓
SO42- dilute HCl, BaCl2 white precipitate SO42-+Ba2+=BaSO4↓
IV. Removal of impurities
Note: In order to make the impurities in addition to the exhaustion, the addition of reagents can not be the "right amount", but should be "too much"; but too much of the reagent must be easy to remove in the subsequent operation.
V. Units of quantity of matter - moles
1. The amount of matter (n) is a physical quantity that represents the collective containing a certain number of particles.
2. Mole (mol): any collective of particles containing 6.02 × 1023 particles measured as 1 mole.
3. Avogadro's constant: Call 6.02 X 1023mol-1 Avogadro's constant.
4. Amount of substance = number of particles contained in a substance / Avogadro's constant n = N/NA
5. Molar mass (M) (1) Definition: The mass of a substance per unit amount of substance is called molar mass. (2) Unit: g/mol or g..mol-1(3) Value: equal to the relative atomic mass or relative molecular mass of the particle.
6. Amount of substance = mass of substance / molar mass ( n = m/M )
VI. Molar volume of gases
1. Molar volume of gases (Vm) (1) Definition: The volume occupied by a gas per unit amount of substance is called the molar volume of the gas. (2) unit: L / mol
2. amount of substance = volume of gas / gas molar volume n = V / Vm
3. standard conditions, Vm = 22.4 L/mol