1. 1, experimental instrument:
Conical flask, long-necked funnel or separating funnel, conduit, water tank, gas container, double-hole plug.
Drugs: manganese dioxide (black solid, chemical formula: MnO2), 5%~6% hydrogen peroxide solution (mixture of 6% H2O2 and 94% water).
Note: Manganese dioxide is a catalyst, which accelerates the decomposition reaction of hydrogen peroxide. The quality and chemical properties of manganese dioxide remain unchanged during the reaction.
1.2, experimental principle
Hydrogen peroxide generates water and oxygen under the catalysis of manganese dioxide.
Text expressions and chemical equations are as follows:
1.3, experimental steps
1.3. 1. Assemble the equipment as shown in the figure below.
Long neck funnel+conical flask
Separating funnel+conical flask
1.3.2, check the air tightness of the device.
Assemble the equipment through the air tightness test (water injection method or liquid difference method) of the long-necked funnel, open the water stop clip, and slowly inject water into the long-necked funnel. When the nozzle of the long-necked funnel is submerged by water, close the water stop clip and continue to inject water. The gas in the conical bottle is squeezed by water, and the air pressure becomes larger, so that the water enters the long-necked funnel, and the water level at the leakage of the long neck is higher than that of the conical bottle, resulting in a liquid level difference, which shows that the air tightness is good.
Assemble the equipment by using the air tightness test of the separating funnel (micro-heating method), close the cock of the separating funnel, put the other end of the catheter into the water, and cover the conical bottle with both hands. After a period of time, if there are bubbles in the water coming out of the conduit port, water will flow into the conduit port to form a water column after being released, indicating that the air tightness is good.
1.3.2, adding drugs
Long-necked funnel+conical flask: firstly, put manganese dioxide into the conical flask, plug the double-hole plug with conduit and long-necked funnel, and add hydrogen peroxide solution into the long-necked funnel to make the end of the long-necked funnel lower than the liquid level to form a liquid seal to prevent gas from escaping from the long-necked funnel.
Separating funnel+conical flask: firstly, put manganese dioxide into conical flask, plug the double-hole plug with conduit and separating funnel, close the cock of separating funnel, open the piston, add hydrogen peroxide into separating funnel, and open the cock to let hydrogen peroxide drip.
1.3.3, oxygen collection
Drainage method: first fill the gas cylinder with water (there can be no bubbles in the gas cylinder), cover the bottle mouth with glass, and then buckle it upside down in the sink. The gas bottle mouth must be placed below the liquid level. When the air bubbles at the mouth of the conduit emerge continuously and evenly, start to collect oxygen, and extend the mouth of the conduit into the gas container filled with water. When you see air bubbles emerging at the outer edge of the gas container mouth, it proves that the collection is full. Cover the mouth of the gas container with ground glass in water and remove it from the water. It's on the table.
Note: after collecting gas with density greater than air, put it directly above the table; After collecting the gas with lower density than air, pour it on the table;
Question: Why can we start collecting oxygen only when the bubbles at the mouth of the catheter come out continuously and evenly?
Answer: There is air in the experimental equipment, and the bubbles just emerged are a mixture of oxygen and air. If the collected oxygen is not pure.
Because oxygen is denser than air, the gas container should be placed directly above the table after it is filled with oxygen.
Upward exhaust method: align the gas bottle mouth to the desktop, extend the conduit to the vicinity of the bottom of the gas bottle, cover the gas bottle mouth with ground glass, and leave some exhaust. After the gas is completely collected, cover the bottle mouth tightly with ground glass. It's on the table.
1.3.4, check whether all oxygen is collected.
Put a stick with Mars into the bottle mouth, and the stick with Mars will be rekindled, indicating that the oxygen has been collected.
2. Experimental phenomenon of hydrogen peroxide oxygen production: there are a lot of bubbles in the conical bottle.