Early Unified State Exam in Chemistry 2017. Task 31

The gas obtained from the calcination of silver (I) nitrate was mixed with another gas obtained from the decomposition of potassium chlorate. The resulting mixture of gases was absorbed by water, and acid was formed. Magnesium phosphide was treated with hydrochloric acid, and gas was released. This gas was carefully passed through a hot concentrated solution of the resulting acid. Write equations for the five reactions described. In your answer, indicate the sum of the coefficients in all equations.

Early Unified State Exam in Chemistry 2017. Task 33

Potassium bicarbonate weighing 45 g was calcined to constant weight. The residue was dissolved in excess sulfuric acid. The resulting gas was passed through 200 g of a 5.6% potassium hydroxide solution. Determine the composition and mass of the formed salt, its mass fraction (%) in the solution. When solving, write down the reaction equations that are indicated in the problem statement and provide all the necessary calculations (indicate the units of measurement of the required physical quantities). In your answer, write down the sum of the molar mass (g/mol) of the salt formed, its mass (g) and its mass fraction (%, rounded to the nearest whole number) in the final solution. Neglect the solubility of gases in water.

Early Unified State Examination in Chemistry 2017. Task 34

Upon combustion of 12.24 g of organic matter of a non-cyclic structure, 20.16 l (n.s.) of carbon dioxide and 12.96 g of water were obtained. It is known that 1 mole of this organic substance adds only 1 mole of water and this substance does not react with an ammonia solution of silver oxide. Based on the data of the problem conditions: 1) make the calculations necessary to establish the molecular formula of an organic substance. 2) compose the molecular formula of an organic substance. 3) draw up a structural formula of an organic substance that unambiguously reflects the order of bonds of atoms in its molecule. 4) write an equation for the hydration reaction of organic matter. In your answer, write down the molar mass (g/mol) of the original organic substance.

On November 14, 2016, approved demonstration versions, codifiers and specifications of control measurement materials for the unified state exam and the main state exam of 2017, including in chemistry, were published on the FIPI website.

Demo version of the Unified State Exam in Chemistry 2017 with answers

Demo versions of the Unified State Examination in Chemistry 2016-2015

There are significant changes in CMM in chemistry in 2017, so demo versions of previous years are provided for reference.

Chemistry – significant changes: The structure of the examination paper has been optimized:

1. The structure of part 1 of CMM has been fundamentally changed: tasks with a choice of one answer have been excluded; The tasks are grouped into separate thematic blocks, each of which contains tasks of both basic and advanced levels of difficulty.

2. The total number of tasks has been reduced from 40 (in 2016) to 34.

3. The rating scale has been changed (from 1 to 2 points) for completing tasks at a basic level of complexity, which test the assimilation of knowledge about the genetic connection of inorganic and organic substances (9 and 17).

4. The maximum initial score for completing the work as a whole will be 60 points (instead of 64 points in 2016).

Duration of the Unified State Exam in Chemistry

The total duration of the examination work is 3.5 hours (210 minutes).

The approximate time allotted for completing individual tasks is:

1) for each task of the basic level of complexity of part 1 – 2–3 minutes;

2) for each task of an increased level of difficulty in part 1 – 5–7 minutes;

3) for each task of a high level of difficulty in part 2 – 10–15 minutes.

A Unified State Examination result in chemistry not lower than the minimum established number of points gives the right to admission to universities in a specialty where the list of entrance tests includes the subject of chemistry.

Universities do not have the right to set the minimum threshold for chemistry below 36 points. Prestigious universities tend to set their minimum threshold much higher. Because to study there, first-year students must have very good knowledge.

On the official website of FIPI, versions of the Unified State Examination in Chemistry are published every year: demonstration, early period. It is these options that give an idea of ​​the structure of the future exam and the level of difficulty of the tasks and are sources of reliable information when preparing for the Unified State Exam.

Early version of the Unified State Exam in Chemistry 2017

Demo version of the Unified State Exam in Chemistry 2017 from FIPI

There are changes in the 2017 versions of the Unified State Exam in Chemistry compared to the previous 2016 KIM, so it is advisable to prepare according to the current version, and to use the versions of previous years for the diversified development of graduates.

Additional materials and equipment

The following materials are attached to each version of the Unified State Examination paper in chemistry:

− periodic table of chemical elements D.I. Mendeleev;

− table of solubility of salts, acids and bases in water;

− electrochemical series of metal voltages.

You are permitted to use a non-programmable calculator during the examination. The list of additional devices and materials, the use of which is permitted for the Unified State Examination, is approved by order of the Russian Ministry of Education and Science.

For those who want to continue their education at a university, the choice of subjects should depend on the list of entrance tests for the chosen specialty
(direction of training).

The list of entrance examinations at universities for all specialties (areas of training) is determined by order of the Russian Ministry of Education and Science. Each university selects from this list certain subjects that it indicates in its admission rules. You need to familiarize yourself with this information on the websites of the selected universities before applying for participation in the Unified State Exam with a list of selected subjects.

The national examination in chemistry is one of the subjects that a graduate can choose independently. This subject is necessary for those students who intend to continue their studies in the field of medicine, chemistry and chemical technology, construction, biotechnology, food industry and similar industries.

It is better to start preparing for this subject in advance, since in this case it will not be possible to leave by cramming. In addition, you need to clarify in advance possible changes and the dates of the exam in order to be able to correctly distribute your efforts during preparation. To make this task as easy as possible for you, we will analyze the features of the Unified State Exam in chemistry in 2017.

Demo version of the Unified State Exam-2017

Unified State Examination dates in chemistry

You can take the chemistry exam on the following dates:

• Early period. The early date for the exam will be 03/16/2017, and 05/3/2017 is declared as a reserve.
• Main stage. The main date for the examination is June 2, 2017.
• Reserve date. 06/19/2017 was selected as a reserve day.

Several categories of persons can take the Unified State Exam before the main deadline, which include:

• evening school students;
• students who are called up to serve in the ranks;
• schoolchildren leaving for a competition, competition or olympiad of federal or international significance,
• eleventh graders who go abroad due to a change of place of residence or to study at a foreign university;
• students who are prescribed preventive, health-improving treatment or rehabilitation procedures on the main date for passing the Unified State Exam;
• graduates of previous years;
• schoolchildren who studied abroad.

Let us remind you that an application for taking the exam early must be written and submitted before March 1, 2017.

Statistical information

The practice of conducting the Unified State Exam shows that chemistry is not particularly popular among graduates. This exam is not easy, so only one student out of ten takes it. The difficulty is also confirmed by the percentage of students who pass this subject with an unsatisfactory grade - in different years this figure ranges from 6.1 to 11% of the total number of schoolchildren taking exams in chemistry.

As for the average exam scores, recently they range from 67.8 (2013) to 56.3 (2015) points. On the one hand, you can notice a downward trend in this indicator, however, on the other hand, we will hasten to reassure students. These scores correspond to the school “B” level, so you shouldn’t be too afraid of chemistry.

What can you use on the Unified State Exam in chemistry?

In the chemistry exam, students can use the periodic table, a table containing information on the solubility of salts, acids and bases, as well as reference materials with data on the electrochemical voltage series of metals. All necessary materials will be given to students along with the ticket. A non-programmable calculator is also mentioned on the Unified State Exam in Chemistry.

Any other items such as smartphones, tablets, players, reference books and programmable computers are prohibited and are grounds for removing the student from the classroom. If you need to go to the first aid station or toilet, it is worth notifying the observer, who will escort you to the right place. Other activities (such as talking to neighbors or changing exam locations) are also prohibited.

Structure of the exam paper

The chemistry ticket consists of 34 tasks, divided into 2 parts:

• the first part includes 29 short-answer tasks;
• the second part consists of 5 tasks, the solution of which will require giving a detailed answer.

When completing chemistry assignments, students must complete the allotted 210 minutes.

Changes in KIM-2017 in chemistry

The national exam in chemistry has undergone a lot of changes, which are reflected in the optimization of the ticket structure. The new KIM is aimed at increasing objectivity when assessing students’ knowledge and practical skills. It is worth paying attention to the following points:

1. In the structure of the first part of the examination sheet, tasks involving the choice of one option from the proposed answers were excluded. New tasks provide a choice of several correct answers from the proposed ones (for example, 2 out of 5 or 3 out of 6), require students to be able to establish correspondence between individual positions from several sets, and also carry out calculations. In addition, the tasks were grouped into separate thematic blocks, each of which contains tasks related to the basic and advanced levels of complexity. In separate blocks, tasks are arranged in increasing complexity, that is, from one to the next the number of actions that need to be performed to obtain an answer will increase. According to a statement by FIPI representatives, these changes will bring the ticket in line with the school chemistry course program and will help students more effectively demonstrate knowledge of the terminology and patterns of chemical processes.
2. In 2017, he reduced the total number of tasks - now there will be not 40, but only 34. Tasks involving similar types of activities have been removed from the ticket: for example, aimed at identifying knowledge about salts, acids and bases and their chemical properties. These changes are explained by the fact that the new ticket is practical-oriented, so even basic tasks will require students to systematically apply the acquired knowledge.
3. Basic level tasks (numbers 9 and 17) test knowledge of the genetic relationships of substances of organic and inorganic nature. Now they are rated not at 1, but at 2 points.
4. The primary score awarded for work has been changed - now it is not 64, but 60 points.

Grading system

Points for the Unified State Examination are assigned based on a maximum of one hundred. They were not transferred to the grading system familiar to schoolchildren until 2017, but this can be done independently.

• If a student scores from 0 to 35 points, his level of knowledge is assessed as unsatisfactory and corresponds to a grade of “2”;
• Scores in the range from 36 to 55 are an indicator of a satisfactory level of knowledge and correspond to the mark “3”;
• Having scored from 56 to 72 points, you can count on a grade of “4”;
• With scores of 73 and above, the rating is considered excellent, that is, “5”.

You can view the final result on the Unified State Exam portal by identifying yourself using your passport data. Let us also recall that the minimum score you need to score for the Unified State Exam in chemistry is 36. It is also worth saying that, according to the latest news, the points for the Unified State Exam in chemistry will influence the grade on the certificate. You should definitely take this chance to correct the mark on your report card that you are not happy with.

Answers and solution - early version in chemistry 2017

To complete tasks 1–3, use the following series of chemical elements. The answer in tasks 1–3 is a sequence of numbers under which the chemical elements in a given row are indicated. 1) S 2) Na 3) Al 4) Si 5) Mg

1) Determine which atoms of the elements indicated in the series contain one unpaired electron in the ground state. Write down the numbers of the selected elements in the answer field

Let us describe the electronic configurations of these elements

S: 1s 2 2s 2 2p 6 3s 2 3p 4

Na: 1s 2 2s 2 2p 6 3s 1

Al:s 2 2s 2 2p 6 3s 2 3p 1

Si:1s 2 2s 2 2p 6 3s 2 3p 2

Mg: 1s 2 2s 2 2p 6 3s 2

We see that the elements Na and Al each have one unpaired electron

In the given transformation scheme X Y Cu CuCl CuI ⎯⎯→ ⎯⎯ 2 → substances X and Y are: 1) AgI 2) I2 3) Cl2 4) HCl 5) KI Write down the numbers of the selected substances under the appropriate letters in the table

2 ) From the chemical elements indicated in the series, select three metal elements. Arrange the selected elements in order of increasing reducing properties. Write down the numbers of the selected elements in the required sequence in the answer field

Reducing properties increase from right to left in groups and from top to bottom in periods; therefore, we will arrange the three metal elements Na, Mg, Al Al, Mg, Na

3) From among the elements indicated in the series, select two elements that, when combined with oxygen, exhibit an oxidation state of +4. Write down the numbers of the selected elements in the answer field.

Let's write down possible compounds with oxygen

4) From the proposed list of substances, select two substances in which an ionic chemical bond is present.

1) KCl 2) KNO3 3) H3BO3 4) H2SO4 5) PCl3

5) Establish a correspondence between the formula of a substance and the class/group to which this substance belongs: for each position indicated by a letter, select the corresponding position indicated by a number.

6) From the proposed list of substances, select two substances, with each of which zinc interacts.

1) nitric acid (solution)

2) iron(II) hydroxide

3) magnesium sulfate (solution)

4) sodium hydroxide (solution)

5) aluminum chloride (solution)

3Zn + 8HNO3= 3Zn(NO3)2 + 4H2O + 2NO

Zn+ 2NaOH +2H2O = Na2 + H2

7 ) From the proposed list of substances, select two oxides that react with water.

Write down the numbers of the selected substances in the answer field.

BaO+H2O= Ba(OH)2

8) A solution of substance Y was added to a test tube with a solution of salt X. As a result of the reaction, the formation of a white precipitate was observed. From the proposed list of substances, select substances X and Y that can enter into the reaction described.

1) hydrogen bromide

3) sodium nitrate

4) sulfur oxide(IV)

5) aluminum chloride

Write down the selected numbers in the table under the corresponding letters.

AlCl3 + 3NH4OH = Al(OH)3+ 3NH4Cl

solution of substance NH3 -> NH3*H2O

9) In a given transformation scheme

Cu—X—- CuCl2—Y—— CuI

substances X and Y are:

Write down the numbers of the selected substances under the corresponding letters in the table

2CuCl2 + 4KI = 2CuI + I2 + 2KCl

10) Establish a correspondence between the reaction equation and the oxidizing substance in this reaction: for each position indicated by a letter, select the corresponding position indicated by a number.

Answer: 1433

11) 1215

30) KI + KIO 3 + H 2 SO 4 = I 2 + K 2 SO 4 + H 2 O

KI due to I -1 reducing agent

KIO 3 due to I +5 oxidizing agent

5KI + KIO 3 + 3H 2 SO 4 = 3I 2 + 3K 2 SO 4 + 3H 2 O

1) 2Cu(NO 3) 2- → 2CuO + 4NO 2 + O 2