The problem of filter residue filtrate in the sprint of the senior high school entrance examination

The middle school entrance examination is only one month away. At this time, the child has to remember that there are too many things to be backed up, but if you have a back, you will be able to correct the questions. Everyone is very feeling about this. In order to let more children lose less points in the test, here will insist on summarizing some solutions and small exercises for the wrong questions in the test. Learn chemistry easily for ten minutes a day.

Today I am going to talk about the problem of filter residue and filtrate. Many children have lost points in this four-tone question. Is the child not a metal activity sequence table? No. So how do you do this type of question?

Problem solving steps:

1. Determine what happens to the system and write a chemical equation. And based on the activity of the metal to judge the occurrence of the reaction.

If the topic has no more information, classify the discussion:

2. The fraction happens to react with one of the substances, and it is discussed in the three cases of complete reaction and incomplete reaction with the two substances. In that way, the conclusions given by the questions are correct and correct.

Use the last multiple-choice question in the 2019 exam to verify the Harbin.

Title: A certain mass of a mixed powder of Al and Fe is added to the AgNO3 solution, and after thorough reaction, it is filtered to obtain a filter residue and a light green filtrate. There are four statements about the filtrate and filter residue:

1 Add dilute hydrochloric acid to the filter residue, and there must be bubbles.

2 Adding dilute hydrochloric acid to the filter residue, there must be a precipitate.

3 The filter residue must contain Ag.

4 The filtrate must contain Fe2, must not contain AgNO3, and may contain Al3.

The correct number of the above statements is

A. 0 B. 1 C. 2 D. 3

Analysis: In the system, Al and Fe react with AgNO3, and a light green solution gives ferrous nitrate. It is also known that there is definitely silver in the filter residue. If the AgNO3 is excessive, the Al and Fe are consumed, and there is definitely a bubble error in the first one. If AgNO3 is insufficient, there must be a precipitation error in 2. 3 correct. 4 Regarding whether silver nitrate is contained or not, we cannot be sure. So 4 errors. The answer is B

In addition to learning to analyze, the accumulation of chemical properties of various substances is also the key. The most important thing is to understand what happens and to judge the phenomenon.

Give everyone a few similar exercises. The probability of such a question being tested is enormous.

1. A certain amount of iron powder is added to the Cu2 solution to fully react, which may occur in the following cases.

1 There are Fe2+, Cu2+ and insoluble materials in the solution are Cu; 2 Fe2+ and Cu2+ in the solution are Fe; in the solution, only Cu2+ and insoluble matter are Fe; in the solution, only Fe2+' insoluble matter is Fe and Cu.

A. 13B. 14C. 23D. 34

2. Both copper and iron are known to react with ferric chloride solutions. The chemical equation for the reaction is as follows:

Cu+2FeCl3=CuCl2+2FeCl2

Fe+2FeCl3=3FeCl2

To the beaker containing the ferric chloride solution, a certain amount of a mixed powder of Cu and Fe was added, and after thorough reaction, it was found that there was still a small amount of solid at the bottom of the beaker and it was filtered. The following judgments are correct.

A. The filtrate must contain CuCl2 and FeCl2B. The filtrate must contain FeCl3

C. The filter residue must contain Cu and FeD. The filter residue must contain Cu and may contain Fe.

Third day: xingjuxiang