slide 2
In the VA-group of the periodic system, the non-metals nitrogenN and phosphorus P, the semi-metal arsenic As, as well as antimony Sb and bismuth Bi, which are classified as non-metals, are located.
slide 3
The atoms of the elements of the VA group have 5 electrons on the outer electron layer. The electronic configuration of their outer electron layer is ns2np3, for example: nitrogen - 2s2p3, phosphorus - 3s23p3.
In chemical compounds, nitrogen and phosphorus atoms can exhibit oxidation states from -3 to +5.
slide 4
nitrogen in nature
Nitrogen is denoted by the symbol N (lat. Nitrogenium, i.e. "giving birth to saltpeter"). The simple substance nitrogen (N2) is a rather inert gas under normal conditions, colorless, tasteless and odorless. Nitrogen, in the form of diatomic N2 molecules, makes up most of the atmosphere, where its content is 78.084% by volume (that is, about 3.87 1015 tons).
slide 5
nitrogen in space
Outside the Earth, nitrogen is found in gaseous nebulae, the solar atmosphere, on Uranus, Neptune, interstellar space, and others. Nitrogen is the 4th most abundant element in the solar system (after hydrogen, helium, and oxygen).
slide 6
Phosphorus in nature
Phosphorus occurs naturally in the form of phosphates. Thus, calcium phosphate Ca3(PO4)2 is the main component of the mineral apatite. Phosphorus is found in all parts of green plants, and even more in fruits and seeds. Contained in animal tissues, is part of proteins and other essential organic compounds (ATP, DNA), is an element of life. Apatite
Slide 7
The simple substance nitrogen consists of diatomic N2 molecules. In the N2 molecule, the nitrogen atoms are linked by a triple covalent nonpolar bond. The triple bond energy is high and amounts to 946 kJ/mol. Therefore, bond breaking and the formation of nitrogen atoms and molecules occurs only at temperatures above 3000°C. The high bond strength in molecules determines the chemical inertness of nitrogen.
Slide 8
In the free state, phosphorus forms several allotropic modifications, which are called white, red and black phosphorus.
Slide 9
In the simplest P4 molecule, each of the four phosphorus atoms is covalently bonded to the other three. White phosphorus consists of such tetrahedral-shaped molecules. Cast in an inert atmosphere in the form of sticks (ingots), it is stored in the absence of air under a layer of purified water or in special inert media.
Slide 10
Chemically, white phosphorus is extremely active! For example, it is slowly oxidized by air oxygen already at room temperature and glows (pale green glow). The phenomenon of this kind of glow due to chemical oxidation reactions is called chemiluminescence (sometimes erroneously phosphorescence). White phosphorus is highly toxic. The lethal dose of white phosphorus for an adult male is 0.05-0.1 g.
slide 11
Red phosphorus has an atomic polymer structure in which each phosphorus atom is bonded to three other atoms by covalent bonds. Red phosphorus is not volatile, insoluble in water, and non-toxic. It is used in the manufacture of matches.
In the light and when heated to 300 ° C without air, white phosphorus turns into red phosphorus.
slide 12
When heated under a pressure of about 1200 times greater than atmospheric pressure, white phosphorus turns into black phosphorus, which has an atomic layered crystal lattice. Black phosphorus is similar to metal in its physical properties: it conducts electricity and glistens. Outwardly, it is very similar to graphite. Black phosphorus is the chemically least active form of phosphorus.
slide 13
In 1830, the French chemist Charles Soria invented phosphorus matches, which consisted of a mixture of barthollet salt, white phosphorus and glue. These matches were very flammable, because they caught fire even from mutual friction in the box and when rubbing against any hard surface, for example, the sole of a boot. Because of white phosphorus, they were poisonous. In 1855, the Swedish chemist Johan Lundström applied red phosphorus to the surface of sandpaper and replaced white phosphorus in the match head with it. Such matches were no longer harmful to health, they easily ignited on a pre-prepared surface and practically did not ignite spontaneously. Johan Lundström patents the first "Swedish match", which has survived almost to this day. In 1855, Lundström's matches were awarded a medal at the World Exhibition in Paris. Later, phosphorus was completely removed from the composition of the match heads and remained only in the spread (grater). With the development of the production of "Swedish" matches, the production of matches using white phosphorus was banned in almost all countries.
Slide 14
The simplest substance, nitrogen N2, is chemically inactive and, as a rule, enters into chemical reactions only at high temperatures. The oxidizing properties of nitrogen are manifested in the reaction with hydrogen and active metals. So, hydrogen and nitrogen combine in the presence of a catalyst at high temperature and high pressure, forming ammonia:
Of the metals, under normal conditions, nitrogen reacts only with lithium, forming lithium nitride:
slide 15
The oxidizing properties of phosphorus are manifested when it interacts with the most active metals:
The reducing properties of nitrogen and phosphorus are manifested when they interact with oxygen. So, nitrogen reacts with oxygen at a temperature of about 3000˚С, forming nitric oxide (II):
slide 16
Phosphorus is also oxidized by oxygen, thus exhibiting reducing properties. But different modifications of phosphorus have different chemical activity. For example, white phosphorus is easily oxidized in air at room temperature to form phosphorus(III) oxide:
Oxidation of white phosphorus is accompanied by luminescence. White and red phosphorus ignite when ignited and burn with a dazzlingly bright flame with the formation of white smoke of phosphorus (IV) oxide:
Slide 17
Burning white phosphorus
Slide 18
The most chemically active, toxic and combustible white phosphorus. Therefore, it is very often used in incendiary bombs. Unfortunately, phosphorus ammunition is also used in the 21st century!
During the siege of Sarajevo, phosphorus shells were used by Bosnian Serb artillery. In 1992, such shells burned down the building of the Institute of Oriental Studies, as a result of which many historical documents were destroyed. - in 2003-2004 they were used by British intelligence services in the vicinity of Basra in Iraq. - in 2004, the United States used against the guerrilla underground in Iraq in the battle for Fallujah. in the summer of 2006, during the Second Lebanon War, artillery shells with white phosphorus were used by the Israeli army. in 2009, during Operation Cast Lead in the Gaza Strip, the Israeli army used ammunition containing white phosphorus, which is allowed by international law. Since 2009 Palestinian terrorists have been loading their missiles with white phosphorus.
Slide 19
The appearance of wandering lights in old cemeteries and swamps is caused by the ignition of phosphine PH3 and other compounds containing phosphorus in air. In air, the products of the combination of phosphorus with hydrogen spontaneously ignite with the formation of a luminous flame and droplets of phosphoric acid, a product of the interaction of phosphorus (V) oxide with water. These droplets create a blurry outline of the "ghost".
Slide 20
The main application of nitrogen is the production of ammonia. Nitrogen is also used to create an inert environment in the drying of explosives and in the storage of valuable paintings and manuscripts. In addition, electric incandescent lamps are filled with nitrogen.
Application of simple substances Production of ammonia Most modern lamps are filled with chemically inert gases. Mixtures of nitrogen N2 with argon Ar are the most common due to their low cost.
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Slides captions:
1. I warn you in advance: I am unbreathable! But everyone seems not to hear And they constantly breathe me. 2. I am a luminiferous element. I'll light a match for you in a moment. They will burn me - and under water my oxide will become acid.
The position of nitrogen and phosphorus in the Periodic system
Characteristics of nitrogen and phosphorus. properties of nitrogen.
Five famous chemists of the XVIII century. gave a certain non-metal, which in the form of a simple substance is a gas and consists of diatomic molecules, five different names. - "poisonous air" - "dephlogisticated air" - "spoiled air" - "suffocating air" - "lifeless air" In 1772, the Scottish chemist, botanist and physician Daniel Rutherford In 1772, the English chemist Joseph Priestley In 1773, the Swedish apothecary chemist Carl Scheele In 1774, the English chemist Henry Cavendish In 1776, the French chemist Antoine Lavoisier
FINDING OF NITROGEN IN NATURE: in a free state in the atmosphere
FINDING OF NITROGEN IN NATURE: in the form of inorganic compounds In small quantities in the soil: in the form of ammonium salts and nitrates. organic Nitrogen of plants and animals (Nucleic acids, proteins)
SIGNS OF COMPARISON NITROGEN PHOSPHORUS POSITION IN PSCE STRUCTURE OF THE ATOM Number of electrons in an atom 7, protons in the nucleus 7, number of neutrons in the nucleus 7 Electronic circuit: 1s 2 2s 2 2p 3 OXIDATION DEGREES 3 period V group main subgroup Serial number 15; relative atomic mass 31 2 period V group Main subgroup Ordinal number 7; relative atomic mass 14 P +15) 2) 8) 5 Number of electrons in an atom 15, protons in the nucleus 15, number of neutrons in the nucleus 16 Electronic circuit: 1s 2 2s 2 2p 6 3s 2 2p 3 N + 7) 2) 5 + 3, +5 , -3 +1,+2,+3,+4, +5 , -3
Determine the oxidation states of nitrogen in the compounds: HNO 3, NH 3, NO, KNO 2, NO 2, N 2 O, HNO 2 s.o. -3 0 +1 +2 +3 +4 +5 compound NH 3 N 2 N 2 O NO N 2 O 3 NO 2 N 2 O 5
STRUCTURE OF THE MOLECULE N N N N BOND: - COVALENT NON-POLE - TRIPLE - STRONG MOLECULE: - VERY STABLE - LOW REACTIVITY 1 3 4 2
N 2 Physical properties: V, C, Z, M slightly lighter than air, t bale = -196 0 C, t pl = -210 0 C
In industry, nitrogen is obtained by distillation of air, in the laboratory - by thermal decomposition of compounds (most often NH 4 NO 2): NH 4 NO 2 → N 2 + 2 H 2 O Phosphorus is obtained by calcining calcium phosphate with coal and sand in electric furnaces at 1500 0 С : 2Ca 3 (PO 4) 2 + 10C + 6SiO 2 → 6CaSiO 3 + 10CO + P 4 Preparation.
Chemical properties of nitrogen Phosphorus with metals at room t reacts with Li 6 Li + N 2 = 2 Li 3 N at high t - with others Me 2Al + N 2 = 2AlN 3Mg + N 2 = Mg 3 N 2 reacts with Me 3 when heated Ca + 2 P \u003d Ca 3 P 2 with oxygen at very high t (about 3000 ° C) N 2 + O 2 \u003d 2 NO white phosphorus ignites spontaneously, and red burns when heated 4 P + 5 O 2 \u003d 2 P 2 O 5 with hydrogen in the presence of a catalyst at high pressure and t N 2 + 3 H 2 = 2 NH 3
Applications Ammonia production Creation of inert atmosphere Creation of low temperatures Saturation of steel surface to increase strength Liquid nitrogen in medicine Synthesis of ammonia Fertilizer industry Synthesis of nitric acid Creation of inert atmosphere N2
Questions for self-control The gas is colorless, tasteless and odorless The molecule is diatomic The content in the air is 78% In the laboratory it is obtained by decomposition of KMnO 4 and H 2 O 2 In industry - from liquid air It is chemically inactive It interacts with almost all simple substances The processes of respiration and photosynthesis are associated with it Is an integral part of proteins Participates in the cycle of substances in nature
CHECK YOURSELF O 2 1, 2, 4, 5, 7, 8, 10. "5" N 2 1, 2, 3, 5, 6, 9, 10. "5" 1-2 errors "4" 3-4 errors « 3 » 5 errors and more « 2 » On the example of information about nitrogen, give arguments in favor of two points of view: 1. Nitrogen - "lifeless" 2. Nitrogen - the main element of life on Earth.
"Compounds of phosphorus" - Oxide of phosphorus. The interaction of phosphoric acid with salts. Phosphoric acid (H3PO4). Chemical properties of phosphorus (V) oxide. The interaction of phosphoric acid with alkalis. Chemical properties. Compound. The interaction of phosphoric acid with metals. Phosphorus compounds. Physical properties of phosphorus (V) oxide.
"Phosphorus Lesson" - Motivational-orientation stage. The history of the discovery of phosphorus. Primary consolidation of acquired knowledge. Phosphorus as an element. Video "Combustion of phosphorus in chlorine." 1682 - R. Boyle in a chemical laboratory when working with phosphorus. Black. Try to determine where is the truth and where is the author's fiction? Allotropy of phosphorus.
"Lesson Compounds of phosphorus" - 1. Orienting and motivational. 2. Operational and executive. 3. Reflective-evaluative. The reagents are red phosphorus. Stage 2. Operational performing. Equipment and didactic material. The position of phosphorus in the Periodic system of D.I. Mendeleev. The teacher motivates students by reading an excerpt from A. Conan Doyle's novel.
"Phosphorus and its compounds" - Conclusions. Phosphorus and its compounds. Ammophos. Precipitate. Phosphorus fertilizers. With a lack of phosphorus, plant diseases develop. Phosphorus compounds in the plant cell. Purpose: to study the effect of phosphorus on the growth and development of plants. Simple superphosphate. The supply of phosphorus to the plant is especially necessary at a young age.
"Characteristics of the element phosphorus" - The glow of white phosphorus. Comparison of the structure of the nitrogen and phosphorus atom. white phosphorus. Getting phosphorus. Oxidizer. Discovered by the German alchemist X. Brand. Burning red phosphorus. Phosphorus burns with a pale green flame. Allotropic modifications of phosphorus. Non-metal. The use of phosphorus. Phosphides are vigorously decomposed by water.
"Element phosphorus" - Interaction with metals. Black phosphorus. To bind calcium compounds, quartz sand is added. Phosphorus. When white phosphorus is heated in an alkali solution, it disproportionates. Interaction with alkalis. white phosphorus. Phosphorus is the 12th most abundant element in nature. Interaction with simple substances - non-metals.
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Class: 9
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Textbook. G.E, Rudzitis, F.G. Feldman. Chemistry. Grade 9
Number of hours: 1 lesson
Lesson type: combined
Teaching methods: informational and illustrative, partially exploratory.
Forms of study: frontal work, independent work in pairs and individual, self-control.
Technology: compiling a basic abstract, using the DER, test control of knowledge.
The purpose of the lesson: Based on the structure, compare the properties of simple substances - nitrogen and phosphorus. Based on the properties, characterize the areas of application of nitrogen and phosphorus, methods for their industrial production.
Lesson objectives:
- Educational:
- consider the structure and physical properties of simple substances - nitrogen and allotropic modifications of phosphorus;
- based on the structure, predict the reactivity of nitrogen and phosphorus, consider the characteristic chemical properties;
- to form the ability to draw up equations of chemical reactions, to consider them from the standpoint of redox properties;
- consider areas of application and industrial methods for producing nitrogen and phosphorus.
- Educational:
- develop the ability to compare, establish causal relationships between the structure of substances and their properties, use, draw conclusions;
- to improve the ability to apply the acquired knowledge to explain various facts and phenomena.
- Educational:
- to cultivate activity, independence, interest in the subject;
- to cultivate the ability to work in pairs, the ability to self-assess the results of activities.
Equipment: computer, projector, multimedia presentation
DURING THE CLASSES
| Slide Description and Presentation Control Explanations | Teacher activity | Student activities |
| organizational stage. (1 minute.) | ||
| Greeting students, checking readiness for the lesson | Students prepare for the lesson (notebooks, textbooks, PSHE) | |
| Knowledge update. Goal setting. (4 min.) | ||
| Slide 1. Comparative characteristics of the elements. Reception of pedagogical technique: insertion of missing words in the text (when you click on the cursor, missing words appear). |
Invites students to give a comparative description of the elements - nitrogen and phosphorus. | Student verbal response: gives a comparative description of the elements nitrogen and phosphorus, using the template on the slide, inserting the missing. |
| Slide 2. Historical background Illustration of portraits of scientists who discovered substances. Clicking on the cursor displays the etymology of the names. |
Motivation to study the topic: students are offered information about the history of the discovery of nitrogen and phosphorus, the etymology of their names. - What properties of nitrogen and phosphorus are reflected in their names? |
Listen to information. Front work: List the known properties of nitrogen and phosphorus. |
| Slide 3. Lesson topic Slide 4. Study plan |
Statement of the educational problem: - What are these properties due to, what other properties do nitrogen and phosphorus exhibit? - Theme of the lesson: "Simple substances - nitrogen and phosphorus" |
Write down the topic, prepare a table. |
| Learning new material. (25 minutes) | ||
| Slide 5. The structure and physical properties of nitrogen and allotropic modifications of phosphorus Hyperlink 1 - slide 6 "Structure and physical properties of white phosphorus" |
The teacher proposes to characterize the structure of the nitrogen molecule and draw a conclusion about the strength of the bond in it. – What type of bond is realized in the nitrogen molecule? How many common electron pairs are formed in a nitrogen molecule? - Make a diagram of the formation of a covalent bond in a nitrogen molecule. Next, the physical properties of nitrogen are considered. Unlike nitrogen, phosphorus can exist in the form of a large number of allotropic modifications, currently there are 11 of them, but the whole variety of species can be reduced to three: white, red and black phosphorus. The teacher explains the phenomenon of allotropy in phosphorus, demonstrates the structure of the crystal lattices of white and red phosphorus, characterizes the physical properties. (hyperlinks1, 2) |
Front work: students answer questions Independent work: write down in a notebook the scheme of bond formation in the nitrogen molecule, its physical properties. They examine the illustrations on the screen, get acquainted with the characteristics of the structure and properties of each modification, make a brief note. |
| Slide 8. Control task A video clip from the film "Phosphorus" is about the Baskervilles' dog. (45 sec) |
The teacher invites students to watch the video and answer the question: - Do you think these events are real? What chemical error did the author make? Justify your answer. |
Front work. Students comment on chemical errors in the proposed video clip, drawing on knowledge about the physical properties of white phosphorus. |
| Slide 9. Predicting the reactivity of nitrogen and phosphorus. When you press the cursor, the outputs appear on the screen |
Students are invited to predict the reactivity of nitrogen and phosphorus based on the structure of substances: - What can be said about the chemical activity of nitrogen? Why? What is the reactivity of phosphorus compared to nitrogen? Why? – Do different modifications of phosphorus exhibit the same reactivity? - What properties, oxidizing or reducing, do nitrogen and phosphorus exhibit in chemical reactions? |
Front work. Based on the structure, students draw conclusions about the low activity of nitrogen and the high reactivity of white phosphorus. A decrease in chemical activity from white phosphorus to black is noted. Make a conclusion about the redox duality of properties. |
| Slide 10. Oxidizing properties of nitrogen and phosphorus Reaction scheme slide. |
It is proposed to draw up equations of reactions that characterize the oxidative properties of nitrogen and phosphorus: with lithium, calcium, hydrogen. (schemes on the slide) The check is carried out by clicking on the mouse button: reaction equations appear on the slide |
|
| Slide 11. Reducing properties of nitrogen and phosphorus Reaction scheme slide. The output of the record of equations for verification is carried out by clicking on the cursor |
It is proposed to draw up equations of reactions that characterize the reducing properties of nitrogen and phosphorus: with oxygen, chlorine. (schemes on the slide) The teacher advises weak students. The check is carried out by clicking on the mouse button: reaction equations appear on the slide |
Independent work in pairs: They write down the reaction equations in a notebook, show the transition of electrons, determine the oxidizing agent and reducing agent. Check, ask questions if they arise. |
| Slide 12. Interaction of red phosphorus with Berthollet salt. On the slide illustration, the reaction scheme. The output of the record of the equation and the electronic balance for verification is carried out by clicking on the cursor |
The teacher talks about the interaction of red phosphorus with potassium chlorate, proposes to write down the reaction equation and arrange the coefficients using the electronic balance method. It checks the formulation of the reaction equation, electronic balance. |
Independent work in pairs: They write down the reaction equation in a notebook, draw up an electronic balance, determine the processes of oxidation, reduction, an oxidizing agent and a reducing agent. Individually perform the control task. |
| Slide 13. Obtaining nitrogen and phosphorus Illustrations. |
Nitrogen occurs in nature in compounds and in the free state, while phosphorus occurs only in compounds. What explains this? - What raw materials are used in industry to produce nitrogen, phosphorus? Next, the teacher talks about industrial methods for obtaining nitrogen and phosphorus. |
They answer questions. Listen to the information, make notes in notebooks. |
| Slides 14, 15. Application of nitrogen and phosphorus. Illustrations. |
Proposes to discuss the scope of nitrogen and phosphorus, based on properties. | Front work: discussion of the fields of application of nitrogen and phosphorus. Briefly write down the areas of application of nitrogen and phosphorus. |
| Control of the assimilation of knowledge. (8 minutes) | ||
| Slide 16. Knowledge control Interactive test: pressing the "question" button opens the wording; the selected answer is pressed; the red icon lights up in case of an incorrect answer, green - in case of a correct one. |
Students are given a test task Attachment 1
) Validation using an interactive test model. |
Individual work on options. Perform a test (6 questions - 5 minutes). Checking the performance of work, evaluation. |
| Homework (2 min) | ||
| Slide 17. Homework §15,16,21 p.52, no.2, p.70 no.2,4,5 Task: Calculate the mass of phosphorus formed from 1 kg of calcium phosphate containing 5% impurities. |
The teacher comments on homework. | Record D/Z |
Smoke without fire
Alkali metals react with ammonia to form amides:
Alkaline earth metals form nitrides
Other hydrogen compounds of nitrogen
A colorless liquid that smells like ammoniaReceipt:
Like ammonia, it exhibits basic properties.
As a base, hydrazine forms two series of hydrazonium salts, for example,
N2H6C12 (dichloride) and N2H5C1 (chloride), the latter can also be obtained
and heating the dichloride:
It is an unstable substance that easily decomposes when heated:
It is a weaker base than ammonia and hydrazine and is
reducing agent, oxidizing to nitric oxide (I) 3. An explosion occurs with ammonia:
4. When in contact with strong oxidizing agents, it acts as a reducing agent:
Chemical properties of NO
NO is a typical reducing agent; it discolors a solution of potassium permanganate:Easily oxidized by atmospheric oxygen. The reaction is very fast because nitric oxide (II)
has an unpaired electron and is essentially a radical:
The reaction leads to the formation of nitric oxide (IV), which has a characteristic reddish-brown
color.
Oxidizing properties are less characteristic (only with strong reducing agents):
On a rhodium catalyst, it oxidizes carbon monoxide to carbon dioxide. Such catalysts are placed in
car exhaust pipes to avoid carbon monoxide pollution.
Biological role:
NO is able to penetrate cell membranes. This molecule plays an important role in the regulation of blood
pressure, muscle relaxation and is involved in a nonspecific immune response. The action of some drugs
for example, nitroglycerin, is based on the formation of this particular molecule.
At the same time, NO is toxic, as it is able to bind to hemoglobin like carbon monoxide and prevent
transport of oxygen and carbon dioxide.
Chemical properties of nitric oxide (IV)
It exists in the form of an equilibrium mixture:Nitric oxide (IV) is an oxide of two acids: nitrous and nitric. Disproportionate in water:
Since the latter acid is stable only in the cold, at room temperature and higher
temperatures, the reaction proceeds in a different way:
However, if a mixture of nitric oxide (IV) and air is passed through water, only nitric oxide is formed.
acid:
Similarly, reactions occur with alkalis: when nitrogen oxide is passed through, a mixture is formed
salts, and if the oxide is passed along with air, then only one salt.
Nitric oxide (IV) is a strong oxidizing agent; sulfur, carbon and metals burn in it.
In the gas phase, it even oxidizes the chloride ion:
There are other nitrogen oxides (III and V), but they are not stable. Nitric acid is a very strong oxidizing agent
under certain conditions, reacts with the majority
inorganic and organic compounds
Interaction with metals
Chemical properties of salts of nitric acid: I. Decomposition of nitrate salts
1. Group IA metals (except lithium nitrate)2. Lithium nitrate and nitrates of other metals (except for mercury nitrates and
silver)
3. Mercury and silver nitrates decompose to pure metal, as they
oxide is unstable
4. The decomposition of metals in lower oxidation states proceeds with
oxidation of this metal
4Fe(NO3)2 2Fe2O3 + 8NO2 + O2
II. Oxidizing properties of nitrate salts
5. Nitrates are part of gunpowder:
6. In solution, they react with metals:
Chemical properties of phosphorus
Qualitative tasks (Doronkin, Berezhnaya)
Continuation
Design tasks Nitrogen tasks
1.2.
3.
4.
5.
6.
7.
A copper plate weighing 1.28 g was lowered into a 63% solution of nitric acid weighing 10 g. Find the mass
10% sodium hydroxide solution, which would completely neutralize the resulting solution. (Answer:
24d).
A mixture of copper (II) nitrate and sodium nitrate weighing 46.1 g was calcined, resulting in a mixture
gases, which was passed through a solution of barium hydroxide. As a result, a salt with a mass of 52.2 g was obtained.
Determine the mass fractions of salts in the initial mixture (81.56% and 18.44%, respectively).
A mixture of carbon and silicon weighing 8 g was added to a 63% solution of nitric acid. Stand out brown
the gas was passed through a solution of potassium hydroxide, while obtaining a solution weighing 484.8 g with a mass
the share of salt is 8.33%. Determine the mass fractions of simple substances in the initial mixture (30% and 70%
respectively).
A piece of magnesium weighing 4.8 g was dissolved in 630 g of a 6% solution of nitric acid, while gaseous
products were not released. Find the mass of a 40% sodium hydroxide solution capable of completely
react with the resulting solution. (55g).
A mixture of aluminum and copper powders was added to a 61% solution of nitric acid at room temperature.
temperature, and observed the release of colored gas with a volume of 26.88 liters. Then to the resulting mixture
an excess of sodium hydroxide solution was added, resulting in gas and a precipitate in molar
ratio 1:2. Determine the mass fractions of metals in the initial mixture. (Answer: 12.3% and 87.7%
respectively.)
Crystalline soda weighing 14.3 g was added to 42 g of nitric acid solution. To received
copper wire was added to the solution, and a colorless gas with a volume of 560 ml was released and in
there are no hydrogen ions left in the solution. Determine the mass fraction of acid in the initial solution.
(Answer: 30%).
Zinc nitrate dihydrate was dissolved in 100 g of water, resulting in 3.62%
salt solution. Then 100 g of 40% sodium hydroxide solution was added there and a solution with
mass fraction of alkali 18%. Determine the mass of the crystalline hydrate. (4.5 g)
Tasks for phosphorus
1.2.
3.
4.
5.
6.
7.
White phosphorus weighing 9.3 g was burned, and the resulting white substance was dissolved in water and heated.
Find the volume of 10% sodium hydroxide solution (density 1.2 g/ml) required to obtain
two acid salts in equal molar ratios. (Answer: 150 ml).
Find the mass of white phosphorus, which, when dissolved in 100 g of 40% hot solution of hydroxide
sodium, so that the mass fraction of alkali in the solution becomes equal to 25.69%. (Answer: 12.4g)
Mixed 340 g of a 5% solution of silver nitrate and 164 g of a 10% solution. Find the minimum volume of 15%
solution (density 1.14 g / ml), which is necessary to dissolve the resulting precipitate. (Answer:
19.1 ml).
392 g of 10% sulfuric acid solution was added to calcium orthophosphate weighing 31 g. Find volume
20% potassium hydroxide solution (density 1.12 g / ml), which is necessary for complete
neutralization of the resulting solution. (Answer: 200 ml).
Phosphorus was burned in an excess of oxygen, and the resulting product was added to 110 g of a 2% solution
sodium hydroxide, thus obtaining acidic and medium salts in a ratio of 1:3. (Answer: 0.62g)
Phosphorus iodide weighing 66.6 g was dissolved in excess water. Determine the mass of a 20% nitrate solution
silver, capable of completely reacting with the resulting solution and the total mass
the precipitate that is formed. (Answer: 680 g of solution and 159.4 g of sediment).
Phosphine weighing 3.4 g was burned, the product of its combustion was dried and added to 160 g of a 10% solution
sodium hydroxide. Determine the mass of a 16% solution of silver nitrate, which can completely
react with the resulting solution. (Answer: 425g).
