Answers and solution - early version in chemistry 2017

To complete tasks 1–3, use the following row 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's write it down electronic configurations element data

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 selected items in ascending order 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(rr)

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

Early Unified State Exam options in chemistry 2016-2015

Changes in the Unified State Exam KIM 2017 compared to 2016

Chemistry – significant changes. Structure optimized exam paper:

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 grading scale has been changed (from 1 to 2 points) for completing assignments basic level difficulties that test the assimilation of knowledge about the genetic relationship of inorganic and organic substances (9 and 17).

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

Structure of KIM Unified State Exam 2017 in Chemistry

Each version of the examination paper is built according to a single plan: the paper consists of two parts, including 34 tasks. Part 1 contains 29 tasks with a short answer, including 20 tasks of a basic level of difficulty (in the version they are numbered: 1–9, 12–17, 20–21, 27–29) and 9 tasks increased level complexity (their serial numbers: 10, 11, 18, 19, 22–26).

Part 2 contains 5 tasks high level complexity, with a detailed answer. These are tasks numbered 30–34.

Total tasks - 34; of which by level of difficulty: B – 20 P – 9; AT 5.

The maximum initial score for the work is 60.

The total time to complete the work is 210 minutes.

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 treated 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 Examination 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 Exam in Chemistry 2017. Task 34

Combustion 12.24 g organic matter of 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 from 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. Write down in your answer molar mass(g/mol) of the original organic substance.

Sodium nitride weighing 8.3 g reacted with sulfuric acid with a mass fraction of 20% and a mass of 490 g. Then crystalline soda weighing 57.2 g was added to the resulting solution. Find the mass fraction (%) of the acid in the final solution. Write down the reaction equations that are indicated in the problem statement, provide all the necessary calculations (indicate the units of measurement of the required physical quantities). Round the answer for the site to the nearest whole number.

Real Unified State Exam 2017. Task 34.

Cyclic substance A (does not contain oxygen or substituents) is oxidized with ring rupture to substance B weighing 20.8 g, the combustion products of which are carbon dioxide volume 13.44 l and water weighing 7.2 g. Based on the data of the task conditions: 1) make the calculations necessary to establish the molecular formula of organic substance B; 2) write down the molecular formulas of organic substances A and B; 3) make up structural formulas organic substances A and B, which unambiguously reflect the order of bonds of atoms in the molecule; 4) write the equation for the oxidation reaction of substance A with a sulfate solution of potassium permanganate to form substance B. In the answer for the site, indicate the sum of all atoms in one molecule of the original organic substance A.