The following experimental phenomena are described incorrectly () A. Red phosphorus burns in the air and white smoke is produced B. Sulfur burns in oxygen and emits a light blue flame C. Bubbles are generated when the iron wire is inserted into dilute hydrochloric acid D. Purple litmus solution turns red after being filled with carbon dioxide

The following experimental phenomena are described incorrectly () A. Red phosphorus burns in the air and white smoke is produced B. Sulfur burns in oxygen and emits a light blue flame C. Bubbles are generated when the iron wire is inserted into dilute hydrochloric acid D. Purple litmus solution turns red after being filled with carbon dioxide

A. Red phosphorus burns in the air and white smoke is produced. Correct;
B. Sulfur burns in oxygen and emits a blue purple flame. Error;
C. Bubbles are generated when the iron wire is inserted into dilute hydrochloric acid. Correct;
D. Purple litmus solution turns red after carbon dioxide is introduced. Correct
Therefore, B

(1) P77-4 junior middle school chemistry: are the following experimental operations correct? You'd better give a reason When dropping liquid, the tip of the dropper shall not touch the inner wall of the test tube that has been added with other reagents

Correct. If you touch the inner wall of the test tube that has been added with other reagents, it will be stained with other reagents, causing pollution and affecting the experimental results

The description of the following experimental phenomena is correct () A. Sulfur burns in the air to form sulfur dioxide B. The wood with Mars revived in the air C. Red phosphorus burns in the air, producing thick white smoke D. Aluminum foil burns in oxygen, releasing a lot of heat and producing dazzling white light

A. Sulfur burns in the air to produce sulfur dioxide, which is an experimental conclusion rather than an experimental phenomenon
B. Wooden strips with sparks cannot be rekindled in the air, so the option is wrong
C. Red phosphorus burns in the air and produces a lot of white smoke instead of white smoke
D. Aluminum foil produces dazzling white light and emits a lot of heat in oxygen
Therefore, D

1. At normal temperature, insert the mercury thermometer into one of the following liquids. After taking out the thermometer and placing it in the air, the indication of the thermometer increases first and then decreases, then it can be judged that the liquid inserted into the thermometer is: A. Salt water B. alcohol C. concentrated sulfuric acid D. concentrated hydrochloric acid 2. For the mixture composed of Mg (OH) 2 and MgO, the mass fraction of magnesium element is measured to be 48%. Take 10g of the mixture and put it into an appropriate amount of dilute sulfuric acid for just complete reaction. What is the mass of solute in the resulting solution?

1. C. concentrated sulfuric acid absorbs water vapor in the air and releases heat to raise the temperature. After heat dissipation, it returns to normal temperature
2. According to the conservation of magnesium
Set the generated MgSO4 mass to X
Mg-----------MgSO4
24--------------120
10*48%--------------X
X=10*0.48*120/24==24g

There is a cup of saturated potassium nitrate solution at 20 ℃. To change its solute mass fraction, the following methods are feasible () A. Add a certain amount of water B. Constant temperature evaporation part of water C. Temperature rise to 60 ℃ D. Add a certain amount of potassium nitrate

A. Adding a certain amount of water to saturated potassium nitrate will increase the mass of solvent and reduce the mass fraction of solute;
B. When saturated potassium nitrate solution evaporates water at constant temperature, the solubility does not change because the temperature does not change, so the mass fraction of solute remains unchanged;
C. When the temperature increases, the saturated solution will become unsaturated solution, but the solute and solvent in the solution do not change, so the mass fraction of solute remains unchanged;
D. When potassium nitrate is added to saturated potassium nitrate solution, it will no longer dissolve because the solution is saturated, so the mass fraction of solute remains unchanged
Therefore: a