The state exam season has started in Russian schools. From March 23 to May 7, early exams are held, and from May 25, the Unified State Examination in the Russian language opens the main wave, which will end in reserve retakes on June 26. Next - receiving certificates, graduations, entering a university!

CMM early Unified State Examination in chemistry you can download for reference. I will post answers and solutions to this option soon.

Some results of the early Unified State Examination in Chemistry, which took place on April 4, 2015, can be summed up now. Examples of written response tasks received from colleagues and students who took exams:

Task 36.
1) KJ+KJO 3 +…=…+K 2 SO 4 +H 2 O
2) Fe(OH)3+…+Br2=K2FeO4+…+H2O
3) Cr(OH)3+J2+…=K2CrO4+…+H2O

Solution:

1) Based on the fact that potassium sulfate is formed on the right side, add sulfuric acid. The oxidizing agent in this reaction is potassium iodate, the reducing agent is potassium iodide. This reaction is an example of counter-disproportionation, when both atoms - the oxidizing agent (J +5) and the reducing agent (J -) - transform into one atom - iodine with an oxidation state of 0.

5KJ + KJO 3 + 3H 2 SO 4 = 3I 2 + 3K 2 SO 4 +3H 2 O

2J — — 2e = J 2 0

2J 5+ +10e = J 2 0

Oxidizing agent - KJO 3 (J +5)

Reductant - KJ (J -).

2) Bromine in an alkaline environment is very strong. Since on the right side there is formed salt iron +6, reaction medium - alkaline, add alkali on the left - potassium hydroxide. Since bromine is an oxidizing agent in this reaction, it is reduced to the oxidation state -1, and in an alkaline environment is written in the form of a salt - potassium bromide.

2Fe(OH) 3 + 10KOH + 3Br 2 = 2K 2 FeO 4 + 6KBr + 8H 2 O

Fe 3+ - 3e = Fe 6+

Br 2 +2e = 2Br -

Oxidizing agent - Br 2 (Br 2)

The reducing agent is Fe(OH) 3 (Fe 3+).

3) Based on the product on the right side - potassium chromate - we determine the alkaline medium in which the reaction is carried out, i.e. add alkali to the left - potassium hydroxide KOH. The oxidizing agent is molecular iodine in an alkaline medium, therefore, it is reduced to iodide ion and written as salt KI:

2Cr(OH) 3 + 3J 2 + 10KOH=2K 2 CrO 4 + 6KI + 8H 2 O

Cr +3 – 3e = Cr +6

J 2 +2e = 2J —

Oxidizing agent - J 2

The reducing agent is Cr(OH) 3 (Cr +3).

Task 37. A solution of copper nitrate was subjected to electrolysis. The substance formed at the cathode reacted with CuO. The resulting substance was treated with concentrated sulfuric acid. A gas with a pungent odor was released. A solution of sodium sulfide was added to this solution, and a black precipitate formed.

Let's take a closer look at the complex oxidation reaction aromatic hydrocarbon with an unsaturated alkyl substituent. Indeed, the reaction is ambiguous, and during the reaction, most likely, a mixture of various oxidation products of organic matter is formed. I’ll immediately make a reservation that everything that is written below relates to the Unified State Exam and the interpretation of this oxidation in the Unified State Exam.

So, why does oxidation occur with the breaking of the sigma and pi bonds? Because oxidation with breaking of only the pi bond (Wagner reaction) in the Unified State Examination is formalized as follows:

Oxidation unsaturated hydrocarbons V aquatic environment and when heated, it occurs with the rupture of sigma and pi bonds (double bonds). At the same time, we also know that the oxidation of benzene homologues produces benzoic acid (in acidic environment) or metal benzoate (in neutral environment). When permanganate is reduced, an alkali is formed. The resulting alkali will neutralize the reaction products. How much it will neutralize them is a question of stoichiometric ratios, i.e. question electronic balance, and answer the question about the composition and quantity of oxidation reaction products of complex organic molecules only possible during the balance sheet process.

In this case, oxidation will most likely proceed according to the following mechanism: potassium benzoate is formed and the S-S connections marked in the figure. The detached carbon atoms are oxidized to carbon dioxide)

The following fragments from textbooks serve as proof of the correctness of this assumption:

Chemistry. 10th grade. Profile level. Kuzmenko, Eremin. 2012, p. 421.

Organic chemistry. Traven V.F., volume 1, 2004, p. 474:

So, we have decided on the products, now we are drawing up a reaction scheme:

The reaction products - carbon dioxide and potassium hydroxide - interact with each other. Since the alkali is in excess, 6 molecules of potassium carbonate are formed and 1 molecule of unreacted potassium hydroxide remains.

Thank you very much, colleagues and readers, for your questions. I will be glad to answer new questions and comments on the materials.

Task 39. 2.3 g of sodium was dissolved in 100 ml of water. 100 ml of 30% nitric acid (p = 1.18 g/ml) was added to the resulting solution. Find mass fraction salts in the final solution.

Task 40. The combustion of 20 g of acyclic organic matter produced 66 g of carbon dioxide and 18 ml of water. This substance reacts with ammonia solution silver oxide, 1 mole of this substance can add only 1 mole of water. Determine the formula and write the reaction with an ammonia solution of silver oxide.

Every option Unified State Examination work in chemistry 2015 consists of two parts, including 40 tasks. Part 1 contains 35 tasks with a short answer, including 26 tasks of a basic level of complexity, the serial numbers of these tasks: 1, 2, 3, 4, ...26, (former A part) and 9 tasks higher level difficulties, serial numbers of these tasks: 27, 28, 29, ... 35 (formerly B part). The answer to each task is written briefly in the form of one number or a sequence of numbers (three or four). The sequence of numbers is written on the answer form without spaces or separating characters.

Part 2 contains 5 tasks high level difficulties with a detailed answer (former C part). The serial numbers of these tasks are: 36, 37, 38, 39, 40. Answers to tasks 36–40 include a detailed description of the entire progress of the task. In answer form No. 2, indicate the task number and write down its complete solution.

For execution exam paper In chemistry, 3 hours (180 minutes) are allotted.
All Unified State Exam forms are filled out in bright black ink. You can use gel, capillary or fountain pens. When completing assignments, you can use a draft. Entries in the draft are not taken into account when grading work.
When doing work on the Unified State Exam in chemistry, you can use Periodic table chemical elements DI. Mendeleev; table of solubility of salts, acids and bases in water; electrochemical series metal stresses.
These accompanying materials are attached to the text of the work. Use a non-programmable calculator for calculations.

Changes in CMM in chemistry in 2015 compared to 2014

In the work of 2015, compared to 2014, the following changes were adopted.

1. The structure of the CMM version has been changed: each version consists of two parts and includes 40 tasks (instead of 42 tasks in 2014), differing in form and level of complexity. The tasks in the variant are presented in continuous numbering mode.

2. The number of tasks at the basic difficulty level has been reduced from 28 to 26 tasks. We combined the former A2 and A3 into task No. 2, A 22 and A23 into task No. 21.
3. The form for recording the answer to each of tasks 1–26 has been changed: in KIM 2015 it is required to write down the number corresponding to the number of the correct answer.
4. The maximum score for completing all tasks of the 2015 examination paper is 64 (instead of 65 points in 2014).
5. The grading scale for the task of finding molecular formula substances. The maximum score for its implementation is 4 (instead of 3 points in 2014). The task has become a little more complicated - it is necessary not only to establish the molecular formula of the original organic substance, but also to compose structural formula of this substance, which uniquely reflects the bond order of the atoms in its molecule and write an additional equation for the reaction of this substance indicated in the problem statement.

It is not at all necessary to pass the Unified State Exam in Chemistry if the graduate does not intend to be a physician or a chemist. Therefore, schoolchildren rarely choose this subject as a subject. The level of difficulty in the exam is increasing, but preparation for the exam sometimes leaves much to be desired. Therefore, the FIPI website ( Federal Institute Pedagogical Measurements) published a demo version of CIMs in 2015. The portal has the ability to download online tests Unified State Exam. We will answer point by point several questions from graduates and their parents who decided to take online testing on the FIPI website.

Demo materials 2015: what is the structure?

The demo has three parts. The first one is a demo version. He is an opportunity to pass trial Unified State Exam in chemistry. The second is a codifier that allows you to determine which topic a certain question relates to. The third is specification, i.e. information about materials and demo options.

How is the demo version different from the offline exam?

Pre-testing has a lot of undoubted advantages. The main one is that you can do it indefinitely. In fact, on a real, even mock exam, only three hours are given for all tasks. To pass it , just click on the appropriate button. By the way, the demo version also contains those CMMs that will actually be encountered in the real exam.

What is a topic codifier?

Sometimes during a trial test the question arises, what topic does this or that question relate to? The coder can easily determine this. Thanks to him, you can “pull up” this or that chemical topic.

Why do we need a specification?

The third section is for neophytes, graduates or people who first learned what CMMs are, that is, control and measuring materials. The specification details the procedures passing the Unified State Exam and the procedure for filling out checklists.

What does the exam consist of?

Demonstration Unified State Exam options in chemistry for 11th grade consist of two parts. The first part includes tasks for which you need to give a short answer. For the tasks from the second part, you must give a detailed answer.

All demo versions of the Unified State Exam in chemistry contain correct answers to all tasks and assessment criteria for tasks with a detailed answer.

IN demo version of the 2020 Unified State Exam in chemistry compared to demo version 2019 in chemistry no changes.

Demo versions of the Unified State Examination in Chemistry

Note that demonstration options in chemistry are presented in pdf format, and to view them you must have, for example, the free Adobe Reader software package installed on your computer.

Changes in demo versions of the Unified State Examination in Chemistry

Demo options Unified State Examination in chemistry for grade 11 for 2002 - 2014 consisted of three parts. The first part included tasks in which you need to choose one of the proposed answers. The tasks from the second part required a short answer. For the tasks from the third part it was necessary to give a detailed answer.

In 2014 in demo version of the Unified State Exam in chemistry the following were introduced changes:

• All calculation problems , the implementation of which was estimated at 1 point, were placed in part 1 of the work (A26–A28),
• topic "Redox reactions" tested using assignments B2 And C1;
• topic "Hydrolysis of salts" was checked only with the help of the task B4;
• a new task has been included(at position B6) to check topics " qualitative reactions on inorganic substances and ions", "qualitative reactions of organic compounds"
• total number of tasks in each version it became 42 (instead of 43 in the 2013 work).

In 2015 there were fundamental changes have been made:

The option became consist of two parts(part 1 - short answer assignments, part 2 - long-answer assignments).

Numbering tasks became through throughout the entire version without letter designations A, B, C.

Was The form of recording the answer in tasks with a choice of answers has been changed: The answer now needs to be written down in a number with the number of the correct answer (rather than marked with a cross).

Was the number of tasks at the basic difficulty level has been reduced from 28 to 26 tasks.

Maximum score for completing all tasks of the 2015 examination paper became 64 (instead of 65 points in 2014).

• The assessment system has been changed tasks to find the molecular formula of a substance. The maximum score for completing it is 4 (instead of 3 points in 2014).

IN 2016 year in demonstration version in chemistrysignificant changes have been made compared to the previous year 2015 :

In part 1 changed the format of tasks 6, 11, 18, 24, 25 and 26 basic level of difficulty with a short answer.

Changed the format of tasks 34 and 35 increased level of difficulty : these tasks now require matching instead of selecting multiple correct answers from a given list.

The distribution of tasks by difficulty level and types of skills tested has been changed.

In 2017 compared to demo version 2016 in chemistrysignificant changes have occurred. The structure of the examination paper has been optimized:

Was the structure of the first part has been changed demo version: tasks with a choice of one answer were excluded from it; the tasks were grouped into separate thematic blocks, each of which began to contain tasks of both basic and advanced levels of complexity.

Was the total number of tasks has been reduced up to 34.

Was grading scale changed(from 1 to 2 points) completing tasks of a basic level of complexity that test the assimilation of knowledge about genetic connection inorganic and organic matter(9 and 17).

Maximum score for completing all tasks of the examination work was reduced to 60 points.

In 2018 in demo version of the Unified State Exam in chemistry compared to demo version 2017 in chemistry the following occurred changes:

Was added task 30 high level of complexity with a detailed answer,

Maximum score for completing all tasks of the examination work remained no change by changing the grading scale for tasks in Part 1.

IN demo versions of the Unified State Exam 2019 - 2020 in chemistry compared to demo version 2018 in chemistry there were no changes.

Documents regulating the structure and content of control tests are presented. measuring materials single state exam in chemistry in 2015: codifier of content elements and requirements for the level of training of graduates educational institutions for holding the unified state exam in 2015; specification of control measuring materials for the Unified State Exam in 2015; demonstration version of control measurement materials of the unified state exam 2015. Document in PDF format.

General changes in the KIM Unified State Exam 2015:

1. The structure of the CMM option has been changed: each option consists of two parts (part 1 - tasks with a short answer, part 2 - tasks with a detailed answer).

2. Tasks in the CMM version are presented in continuous numbering mode without letter designations A, B, C.

3. The form of recording the answer in tasks with a choice of one answer has been changed: as in tasks with a short answer, the number of the correct answer is written in digits (not a cross).

4. By majority educational subjects The number of tasks with a choice of one answer has been reduced.

5. Based on the analysis of statistical data on the exam results and the quality of the CMM, in a number of subjects, some lines of tasks were excluded, and the form of a number of tasks was changed.

6. Work is ongoing on an ongoing basis to improve the evaluation criteria for tasks with a detailed answer.

There are no fundamental changes in the planned KIM Unified State Exam 2014 in chemistry.

1. The number of tasks at the basic difficulty level has been reduced from 28 to 26 tasks.

2. The form for recording the answer to each of tasks 1-26 has been changed: in KIM 2015 it is required to write down the number corresponding to the number of the correct answer.

3. The maximum score for completing all tasks of the 2015 examination paper is 64 (instead of 65 points in 2014).

4. The assessment system for the task of finding the molecular formula of a substance has been changed. The maximum score for its implementation is 4 (instead of 3 points in 2014).

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On the topic: methodological developments, presentations and notes

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