9 CLASS
Continuation. See No. 34, 35, 36, 37, 38/2003
Practical work number 13.
Nitric acid. Nitrates
(the ending)
HNO 3 is a strong oxidizing agent. Concentrated nitric acid oxidizes non-metals to higher oxidation states:
Passivation occurs due to the formation of insoluble metal oxide films:
2Al + 6HNO 3 \u003d Al 2 O 3 + 6NO 2 + 3H 2 O.
HNO 3 (conc.) can be stored and transported without air access in containers made of Fe, Al, Ni.
A qualitative reaction is the interaction of HNO 3 with Cu with the formation of brown NO 2 gas with a pungent odor (in addition, salt and water are formed).
As the concentration (dilution) decreases, HNO 3 with Zn can form various nitrogen-containing products:
and in all cases salt and water.
Note
. To recognize the nitrate anion, a diphenylamine indicator is used (a solution of (C 6 H 5) 2 NH in conc. H 2 SO 4).
Demo Experience
. Recognition is carried out “on traces” or by drop contact: a dark blue color appears.
Nitrates- salts of nitric acid, crystalline solids, highly soluble in water. Nitrates of alkali metals, calcium and ammonium - saltpeter.
Most nitrates are very good mineral fertilizers.
Nitrates are strong oxidizing agents! Coal, sulfur and other combustible substances burn in molten saltpeter, since all nitrates (like HNO 3) release oxygen when heated and, depending on the chemical activity of the salt metal, give different products:
| Operating procedure | Tasks | Observations and Conclusions |
|---|---|---|
| Assemble the device (according to the scheme), put a little crystalline sodium (Chile) nitrate in a cup, melt it. Heat a piece of charcoal in the flame of an alcohol lamp and lower it into molten saltpeter
|
Why does coal ignite? Write the equations of the ongoing reactions based on the electronic balance, draw the appropriate conclusions | |
| Take samples of all three solutions in test tubes No. 1–3 (see No. 38/2003) and first add approximately an equal amount (volume) of concentrated sulfuric acid to each sample, then add a little copper shavings, warm up a little. Observe characteristic changes in one of the samples | Three numbered tubes contain solutions of chloride, sulfate and sodium nitrate. Recognize saltpeter solution. Why is concentrated sulfuric acid first added to a nitrate solution? Write the molecular and ionic reaction equations. Check the output by reaction "for traces" with a diphenylamine indicator |
Complex substances (turpentine, wood, sawdust) can also burn in nitric acid. A mixture of concentrated nitric and sulfuric acids (nitrating mixture) with many organic substances forms nitro compounds (nitration reaction).
A mixture of 1 volume HNO 3 (conc.) and 3 volumes HCl (conc.) is called "aqua regia". Even gold Au and platinum Pt dissolve in such a mixture:
| Operating procedure | Tasks | Observations and Conclusions |
|---|---|---|
| In a test tube with concentrated nitric acid (1 ml), add some copper shavings (Cu). With a delayed effect, warm up a little. Work under draft! Pour products from a sanitary bottle into the sewer system and rinse with a stream of water | What explains the evolution of brown gas with a pungent odor? Considering that water and copper (II) nitrate are still formed in this case, write the reaction equation. Draw an electronic balance diagram and write the reaction equation in ionic form | |
| Mix powder of fine-grained sulfur (S) with 1 ml of concentrated HNO 3, heat the mixture (under draft). Take a sample of the reaction products and test it with 2-3 drops of barium chloride solution. Pour the products from the sanitary bottle into the sewer system immediately | What explains the observed changes - the dissolution of sulfur, the release of a brown, sharp-smelling gas (and water)? Write an equation for this reaction. Draw up an electronic balance diagram and an ionic equation for the reaction. What do the changes observed during the interaction of a sample of reaction products with a solution of barium chloride prove? Justify your answer |
Practical work 14.
Determination of orthophosphates
Goals. Learn to recognize orthophosphates, hydrogen orthophosphates and dihydroorthophosphates by their solubility in water, hydrolysis, and qualitative reaction to the orthophosphate anion.
Equipment and reagents. Stand with test tubes, glass tubes with rubber rings, sanitary flask, spatulas (3 pcs.); crystalline Ca 3 (PO 4) 2, CaHPO 4, Ca (H 2 PO 4) 2, distilled water, a universal indicator, solutions of H 3 PO 4, NaCH 3 COO ( \u003d 10%), AgNO 3.
| Operating procedure | Tasks | Observations and Conclusions |
|---|---|---|
| Pour 1 cm 3 of calcium orthophosphate, hydrogen orthophosphate and calcium dihydrogen orthophosphate into three test tubes, add a little (the same amount) of water, mix | Make a conclusion about the solubility of primary, secondary and tertiary orthophosphates. Can the different solubility of these phosphates be considered a method for their recognition? | … |
| Using aqueous solutions and suspensions in three test tubes of previous experience, test them with a universal indicator | Determine on the pH scale of all solutions and explain why the pH in this case has different values | … |
| K an aqueous solution of phosphoric acid in one test tube (1 ml) and a solution of superphosphate in another (1 ml) add 10% sodium acetate solution and a few drops of silver(I) nitrate |
What is a reactive ion? Write the equations of the corresponding reactions in molecular and ionic forms, indicate the signs of reactions | … |
Practical work 15.
Determination of mineral fertilizers.
Solving experimental problems on the topic
"Nitrogen subgroup"
Goals. Repeat the composition and properties of nitrogen and phosphorus compounds, their interconversions and methods of recognition.
Equipment and reagents. Spirit lamp, matches, blue glass, filter paper, test tube holder, test tube stand (2 pcs.), spatulas (3 pcs.), mortar, pestle, sanitary bottle;
in test tubes No. 1–3:
I option
- double superphosphate, NH 4 NO 3, (NH 4) 2 SO 4,
II option
- NH 4 Cl, NaNO 3, KCl,
III option
- KNO 3, (NH 4) 2 SO 4, double superphosphate;
crystalline salts (NH 4) 2 SO 4, NH4Cl, ammophos, aqueous solutions of CH 3 COONa (= 10%), AgNO 3, BaCl 2,
CH 3 COOH (= 10%), NaOH, litmus paper, CuO, Cu (shavings), HNO 3 (razb.), HNO 3 (conc.), H 2 SO 4 (conc.), diphenyl indicator, (C 6 H 5) 2 NH in concentrated H 2 SO 4,
Ca(OH) 2 (dry), distilled water, AgNO 3 in HNO 3 , in test tubes No. 4–6 dry crystalline substances: Na 2 SO 4 , NH 4 Cl, NaNO 3 , in test tubes No. 7 and 8: H 3 PO 4 and H 2 SO 4 (sorted solutions), in test tubes No. 9 and 10: Na 3 PO 4 and Ca 3 (PO 4) 2 .
Experimental problem . Four numbered flasks contain aqueous solutions of sodium orthophosphate, ammonium sulfate, sodium nitrate, potassium chloride. Using the most rational recognition methods (see table), determine where each substance is located.
Characteristic features of some salts
(recognition methods)
Table
| Substance name | Appearance | Solubility (in water) | The interaction of a solution of this salt with | Flame coloring | |||
|---|---|---|---|---|---|---|---|
| H 2 SO 4 (conc.) and Cu |
solutions of BaCl 2 and CH 3 COOH | NaOH solution when heated | AgNO 3 solution | ||||
| Ammonium nitrate NH 4 NO 3 | Good | NO 2 , brown, with a pungent odor | – | NH 3 , colorless, with a pungent odor | – | yellow (from impurities) |
|
| Ammonium chloride NH 4 Cl | White crystalline powder | Good | – | – | NH3 | AgCl, white precipitate | yellow (from impurities) |
| Potassium nitrate KNO 3 | Light gray fine crystals | Good | NO 2 | – | – | – | purple |
| Ammonium sulfate (NH 4) 2 SO 4 | Colorless large crystals | Good | – | BaSO 4 , white, insoluble in CH 3 COOH | NH3 | Ag 2 SO 4 , white, readily soluble in acids | – |
| Superphosphate Ca (H 2 PO 4) 2 2H 2 O | Light gray powder or granules | Dissolves slowly | – | Ba 3 (PO 4) 2, white, partially soluble in CH 3 COOH |
– | Ag 3 PO 4 , yellow (in the presence of CH 3 COOHa) | Brick- red |
| Silvinite KCl NaCl | pink crystals | Good | – | – | AgCl | Yellow with hints of purple | |
| Potassium chloride KCl | Colorless crystals | Good | – | – | – | AgCl | purple |
Decision
All ions in the aquatic environment colorless, it is impossible to recognize them by color.
2) Since none of the substances (flasks No. 1–4) differ in worse solubility, solutions cannot be distinguished by this feature, all are transparent solutions.
3) In two solutions there are identical cations, but in all - different anions, therefore, qualitative recognition should be carried out by anions. Reactive - AgNO 3 in the presence of a 10% solution of CH 3 COOHa (or BaCl 2 and CH 3 COOH); reagent - BaCl 2 solution; reagent for Cl – solution of AgNO 3 in HNO 3 ; reagent - concentrated H 2 SO 4 and Cu (shavings). You can immediately identify, then, using one reagent (AgNO 3), recognize all three remaining solutions (or vice versa). Other options are longer and require a significantly higher consumption of reagents.
4) Test all four samples of solutions with a solution of AgNO 3 (1-2 drops): the solution from bottle No. 4 remained unchanged - it should be a solution of NaNO 3; in flask No. 2, a white crystalline precipitate, insoluble in acids, is a solution of KCl; the other two samples give cloudy solutions, when a 10% solution of CH 3 COOHa is added, sample No. 3 gives a yellow precipitate - this is a Na 3 PO 4 solution, and sample No. 1 is a solution of (NH 4) 2 SO 4 (turbidity disappears when adding acid HNO 3).
Verification of primary tests.
Add 1–2 drops of BaCl 2 and CH 3 COOH solutions to the solution sample from flask No. 1, the solution becomes milky in color, because a white crystalline precipitate precipitates:
You can check the same sample by adding an alkali solution with heating. NH 3 gas is released, which is determined by the characteristic smell and blue of wet red litmus paper. Reaction equation:
Add concentrated H 2 SO 4 and Cu (shavings) to the solution sample from bottle No. 4, heat it up a little. A brown gas with a pungent odor is released, and the solution becomes greenish-azure:
5) Conclusion .
In flasks:
No. 1 - solution (NH 4) 2 SO 4,
No. 2 - KCl solution,
No. 3 - Na 3 PO 4 solution,
No. 4 - NaNO 3 solution.
Recognition scheme
Determined solutions |
|||
| № 1 | № 2 | № 3 | № 4 |
| (NH 4) 2 SO 4 | KCl | Na3PO4 | NaNO 3 |
| All solutions are clear and colorless. | |||
| +AgNO3 | |||
| Turbidity of the solution (Ag 2 SO 4, soluble in acids) |
White cheesy precipitate (AgCl | According to the variant, write down the solutions of which salts are given in test tubes No. 1–3. Determine where each of these substances is located. In the conclusions, write down the equations of the reactions carried out in molecular and ionic forms. Mark the signs of each qualitative reaction | … |
| 1) In a test tube with a small amount of CuO (at the tip of a spatula), add a solution of HNO 3, shake. 2) Put a few copper shavings into a test tube with concentrated HNO 3 (if the effect is not immediately observed, warm the mixture a little) |
Using the given reagents, prepare a solution of copper(II) nitrate in two ways. Mark signs of reactions and write molecular and ionic reaction equations. Which reaction is a redox reaction? |
… | |
| In a mortar, mix and grind the mixture of Ca (OH) 2 (slightly moistened) with ammonium salt, gently smell. Repeat the experiment with other ammonium salts |
Empirically prove that sulfate, ammonium nitrate and chloride must not be mixed with lime. Give appropriate explanations |
… | |
| Draw up a plan (order) for recognition, the most rational in terms of time and consumption of reagents | In test tubes No. 4–6, determine crystalline sodium sulfate, ammonium chloride and sodium nitrate. Write reaction equations. Note observed signs of reactions |
... | |
| It is best to test samples of solutions in test tubes No. 7 and 8 with BaCl 2 and CH 3 COOH reagents, very carefully observing the result when shaking the reaction mixture |
By qualitative recognition to determine in which of test tubes No. 7 and 8 are solutions sulfuric and phosphoric acids. Write reaction equations |
... | |
| Make a plan for the recognition of substances Na 3 PO 4 and Ca 3 (PO 4) 2 in test tubes No. 9 and 10 |
Determine practically in test tubes No. 9 and 10 crystalline sodium and calcium orthophosphates |
... | |
Definition salts within the framework of the theory of dissociation. Salts are usually divided into three groups: medium, sour and basic. In medium salts, all hydrogen atoms of the corresponding acid are replaced by metal atoms, in acid salts they are only partially replaced, in basic salts of the OH group of the corresponding base they are partially replaced by acid residues.
There are also some other types of salts, such as double salts, which contain two different cations and one anion: CaCO 3 MgCO 3 (dolomite), KCl NaCl (sylvinite), KAl (SO 4) 2 (potassium alum); mixed salts, which contain one cation and two different anions: CaOCl 2 (or Ca(OCl)Cl); complex salts, which include complex ion, consisting of a central atom linked to several ligands: K 4 (yellow blood salt), K 3 (red blood salt), Na, Cl; hydrated salts(crystal hydrates), which contain molecules water of crystallization: CuSO 4 5H 2 O (copper sulfate), Na 2 SO 4 10H 2 O (Glauber's salt).
The name of the salts is formed from the name of the anion followed by the name of the cation.
For salts of oxygen-free acids, a suffix is added to the name of the non-metal id, e.g. sodium chloride NaCl, iron(H) sulfide FeS, etc.
When naming salts of oxygen-containing acids, in the case of higher oxidation states, the ending is added to the Latin root of the name of the element — am, in the case of lower oxidation states, the ending -it. In the names of some acids, the prefix is used to designate the lowest oxidation states of a non-metal hypo-, for salts of perchloric and permanganic acids, use the prefix per-, ex: calcium carbonate CaCO 3, iron (III) sulfate Fe 2 (SO 4) 3, iron (II) sulfite FeSO 3, potassium hypochlorite KOSl, potassium chlorite KOSl 2, potassium chlorate KOSl 3, potassium perchlorate KOSl 4, potassium permanganate KMnO 4, potassium dichromate K 2 Cr 2 O 7 .
Acid and basic salts can be considered as a product of incomplete conversion of acids and bases. According to the international nomenclature, the hydrogen atom, which is part of the acid salt, is denoted by the prefix hydro-, OH group - prefix hydroxy, NaHS - sodium hydrosulfide, NaHSO 3 - sodium hydrosulfite, Mg (OH) Cl - magnesium hydroxychloride, Al (OH) 2 Cl - aluminum dihydroxy chloride.
In the names of complex ions, ligands are first indicated, followed by the name of the metal, indicating the corresponding oxidation state (Roman numerals in brackets). In the names of complex cations, Russian names of metals are used, for example: Cl 2 - tetraammine copper (P) chloride, 2 SO 4 - diammine silver (1) sulfate. In the names of complex anions, the Latin names of metals with the suffix -at are used, for example: K[Al (OH) 4] - potassium tetrahydroxyaluminate, Na - sodium tetrahydroxychromate, K 4 - potassium hexacyanoferrate (H) .
Names of hydrated salts (crystalline hydrates) are formed in two ways. You can use the complex cation naming system described above; for example, copper sulfate SO 4 H 2 0 (or CuSO 4 5H 2 O) can be called tetraaquacopper(II) sulfate. However, for the most well-known hydrated salts, most often the number of water molecules (degree of hydration) is indicated by a numerical prefix to the word "hydrate", for example: CuSO 4 5H 2 O - copper (I) sulfate pentahydrate, Na 2 SO 4 10H 2 O - sodium sulfate decahydrate, CaCl 2 2H 2 O - calcium chloride dihydrate.
Solubility of salts
According to their solubility in water, salts are divided into soluble (P), insoluble (H) and slightly soluble (M). To determine the solubility of salts, use the table of the solubility of acids, bases and salts in water. If there is no table at hand, then you can use the rules. They are easy to remember.
1. All salts of nitric acid are soluble - nitrates.
2. All salts of hydrochloric acid are soluble - chlorides, except for AgCl (H), PbCl 2 (M).
3. All salts of sulfuric acid - sulfates are soluble, except for BaSO 4 (H), PbSO 4 (H).
4. Sodium and potassium salts are soluble.
5. All phosphates, carbonates, silicates and sulfides do not dissolve, except for Na salts + and K + .
Of all chemical compounds, salts are the most numerous class of substances. These are solids, they differ from each other in color and solubility in water. At the beginning of the XIX century. Swedish chemist I. Berzelius formulated the definition of salts as reaction products of acids with bases or compounds obtained by replacing hydrogen atoms in an acid with a metal. On this basis, salts are distinguished as medium, acidic and basic. Medium, or normal, salts are products of the complete replacement of hydrogen atoms in an acid with a metal.
For example:
Na 2 CO 3 - sodium carbonate;
CuSO 4 - copper (II) sulfate, etc.
Such salts dissociate into metal cations and anions of the acid residue:
Na 2 CO 3 \u003d 2Na + + CO 2 -
Acid salts are products of incomplete replacement of hydrogen atoms in an acid by a metal. Acid salts include, for example, baking soda NaHCO 3 , which consists of a metal cation Na + and an acid singly charged residue HCO 3 - . For an acidic calcium salt, the formula is written as follows: Ca (HCO 3) 2. The names of these salts are made up of the names of medium salts with the addition of the prefix hydro- , For example:
Mg (HSO 4) 2 - magnesium hydrosulfate.
Dissociate acid salts as follows:
NaHCO 3 \u003d Na + + HCO 3 -
Mg (HSO 4) 2 \u003d Mg 2+ + 2HSO 4 -
Basic salts are products of incomplete substitution of hydroxo groups in the base for an acid residue. For example, such salts include the famous malachite (CuOH) 2 CO 3, which you read about in the works of P. Bazhov. It consists of two basic cations CuOH + and a doubly charged anion of the acid residue CO 3 2- . The CuOH + cation has a +1 charge, therefore, in the molecule, two such cations and one doubly charged CO 3 2- anion are combined into an electrically neutral salt.
The names of such salts will be the same as for normal salts, but with the addition of the prefix hydroxo-, (CuOH) 2 CO 3 - copper (II) hydroxocarbonate or AlOHCl 2 - aluminum hydroxochloride. Most basic salts are insoluble or sparingly soluble.
The latter dissociate like this:
AlOHCl 2 \u003d AlOH 2 + + 2Cl -
Salt properties
The first two exchange reactions have been discussed in detail previously.
The third reaction is also an exchange reaction. It flows between salt solutions and is accompanied by the formation of a precipitate, for example:
The fourth reaction of salts is associated with the position of the metal in the electrochemical series of metal voltages (see "Electrochemical series of metal voltages"). Each metal displaces from salt solutions all other metals located to the right of it in a series of voltages. This is subject to the following conditions:
1) both salts (both reacting and formed as a result of the reaction) must be soluble;
2) metals should not interact with water, therefore, metals of the main subgroups of groups I and II (for the latter, starting with Ca) do not displace other metals from salt solutions.
Methods for obtaining salts
Methods for obtaining and chemical properties of salts. Salts can be obtained from inorganic compounds of almost any class. Along with these methods, salts of anoxic acids can be obtained by direct interaction of a metal and a non-metal (Cl, S, etc.).
Many salts are stable when heated. However, ammonium salts, as well as some salts of low-active metals, weak acids and acids in which elements exhibit higher or lower oxidation states, decompose when heated.
CaCO 3 \u003d CaO + CO 2
2Ag 2 CO 3 \u003d 4Ag + 2CO 2 + O 2
NH 4 Cl \u003d NH 3 + HCl
2KNO 3 \u003d 2KNO 2 + O 2
2FeSO 4 \u003d Fe 2 O 3 + SO 2 + SO 3
4FeSO 4 \u003d 2Fe 2 O 3 + 4SO 2 + O 2
2Cu(NO 3) 2 \u003d 2CuO + 4NO 2 + O 2
2AgNO 3 \u003d 2Ag + 2NO 2 + O 2
NH 4 NO 3 \u003d N 2 O + 2H 2 O
(NH 4) 2 Cr 2 O 7 \u003d Cr 2 O 3 + N 2 + 4H 2 O
2KSlO 3 \u003d MnO 2 \u003d 2KCl + 3O 2
4KClO 3 \u003d 3KSlO 4 + KCl
oxides. Nitrogen forms five oxides with oxidation states +1, +2, +3, +4, +5.
Oxides N 2 O and NO are non-salt-forming (what does this mean?), And the rest of the oxides are acidic: corresponds to nitrous acid, a - nitric acid. Nitric oxide (IV), when dissolved in water, simultaneously forms two acids - HNO 2 and HNO 3:
2NO 2 + H 2 O \u003d HNO 2 + HNO 3.
If it is dissolved in water in the presence of excess oxygen, only nitric acid is obtained:
4NO 2 + O 2 + 2H 2 O \u003d 4HNO 3.
Nitric oxide (IV) NO 2 is a brown, very poisonous gas. It is easily obtained by oxidizing colorless, non-salt-forming nitric oxide (II) with oxygen in the air:
2NO + O 2 \u003d 2NO 2.
Nitric acid HNO 3 . It is a colorless liquid that "fumes" in air. When stored in the light, concentrated nitric acid turns yellow, as it partially decomposes with the formation of brown NO 2 gas:
4HNO 3 \u003d 2H 2 O + 4NO 2 + O 2.
Nitric acid exhibits all the typical properties of strong acids: it interacts with oxides and hydroxides of metals, with salts (make the appropriate reaction equations).
Laboratory experiment No. 32
Properties of dilute nitric acid
Make experiments proving that nitric acid exhibits the typical properties of acids.
|
With metals, nitric acid behaves in a special way - none of the metals displaces hydrogen from nitric acid, regardless of its concentration (for sulfuric acid, this behavior is typical only in its concentrated state). This is due to the fact that HNO 3 is a strong oxidizing agent, in it nitrogen has a maximum oxidation state of +5. It is he who will be restored when interacting with metals.
The reduction product depends on the position of the metal in the stress series, on the concentration of the acid, and on the reaction conditions. For example, when interacting with copper, concentrated nitric acid is reduced to nitric oxide (IV):
Laboratory experiment No. 33
Interaction of concentrated nitric acid with copper
| Carefully pour 1 ml of concentrated nitric acid into a test tube. Scoop up a little copper powder with the tip of a glass tube and pour it into a test tube with acid. (If there is no copper powder in the cabinet, you can use a small piece of very thin copper wire, which must first be rolled into a ball.) What are you observing? Why does the reaction proceed without heating? Why does this version of the experiment not require the use of a fume hood? If the area of contact of copper with nitric acid is less than the proposed version of the experiment, then what conditions must be observed? After the experiment, immediately place the test tubes with the contents in a fume hood. Write down the reaction equation and consider redox processes. |
Iron and aluminum, under the action of concentrated HNO 2, are covered with a strong oxide film that protects the metal from further oxidation, i.e., the acid passivates the metals. Therefore, nitric acid, like sulfuric acid, can be transported in steel and aluminum tanks.
Nitric acid oxidizes many organic substances, discolors dyes. In this case, a lot of heat is usually released and the substance ignites. So, if a drop of turpentine is added to nitric acid, then a bright flash occurs, and a smoldering splinter in nitric acid lights up (Fig. 135).
Rice. 135.
Burning a splinter in nitric acid
Nitric acid is widely used in the chemical industry for the production of nitrogen fertilizers, plastics, artificial fibers, organic dyes and varnishes, medicinal and explosives (Fig. 136).
Rice. 136.
Nitric acid is used to produce:
1 - fertilizers; 2 - plastics; 3 - medicines; 4 - varnishes; 5 - artificial fibers; 6 - explosives
Salts of nitric acid - nitrates are obtained by the action of acid on metals, their oxides and hydroxides. Sodium, potassium, calcium and ammonium nitrates are called saltpeters: NaNO 3 - sodium nitrate, KNO 3 - potassium nitrate, Ca (NO 3) 2 - calcium nitrate, NH 4 NO 3 - ammonium nitrate. Saltpeter is used as nitrogen fertilizer.
Potassium nitrate is also used in the manufacture of black powder, and ammonium nitrate, as you already know, is used to prepare the ammonal explosive. Silver nitrate, or lapis, AgNO 3 is used in medicine as a cauterizing agent.
Almost all nitrates are highly soluble in water. When heated, they decompose with the release of oxygen, for example:
New words and concepts
- Non-salt-forming and acidic nitrogen oxides.
- Nitric oxide (IV).
- Properties of nitric acid as an electrolyte and as an oxidizing agent.
- Interaction of concentrated and dilute nitric acid with copper.
- Application of nitric acid.
- Nitrates, saltpeters.
Tasks for independent work
- Why does nitric acid not form acid salts?
- Write the molecular and ionic equations for the reactions of nitric acid with copper(II) hydroxide, iron(III) oxide, and sodium carbonate.
- Most salts of nitric acid are soluble in water, however, offer an equation for the reaction of HNO 3 with salt, as a result of which a precipitate forms. Write the ionic equation for this reaction.
- Consider the reaction equations for dilute and concentrated nitric acid with copper in terms of redox processes.
- Propose two chains of transformations leading to the production of nitric acid, starting from nitrogen and ammonia. Describe redox reactions using the electron balance method.
- How many kilograms of 68% nitric acid can be obtained from 276 kg (n.a.) nitric oxide (IV)?
- When calcining 340 g of sodium nitrate, 33.6 liters (n.a.) of oxygen were obtained. Calculate the mass fraction of impurities in saltpeter.
In order to depict the salt formula graphically, one should:
1. Correctly write the empirical formula of this compound.
2. Considering that any salt can be represented as a product of neutralization of the corresponding acid and base, the formulas of the acid and base that form this salt should be shown separately.
For example:
Ca (HSO 4) 2 - calcium hydrosulfate can be obtained by incomplete neutralization of sulfuric acid H 2 SO 4 with calcium hydroxide Ca (OH) 2.
3. Determine how many acid and base molecules are required to obtain a molecule of this salt.
For example:
To obtain a Ca(HSO 4) 2 molecule, one base molecule (one calcium atom) and two acid molecules (two HSO 4 - 1 acid residues) are required.
Ca (OH) 2 + 2H 2 SO 4 \u003d Ca (HSO 4) 2 + 2H 2 O.
Next, you should build graphic images of the formulas of the established number of base and acid molecules and, mentally removing the base hydroxyl anions and acid hydrogen cations participating in the neutralization reaction and forming water, get a graphic image of the salt formula:
O – H H - O O O O
Ca 
+ → Ca + 2 H - O - H
O – H H - O O O O
H-O O H-O O
Physical properties of salts
Salts are crystalline solids. According to their solubility in water, they can be divided into:
1) highly soluble,
2) slightly soluble,
3) practically insoluble.
Most salts of nitric and acetic acids, as well as potassium, sodium and ammonium salts are soluble in water.
Salts have a wide range of melting and thermal decomposition temperatures.
Chemical properties of salts
The chemical properties of salts characterize their relationship to metals, alkalis, acids and salts.
1. Salts in solutions interact with more active metals.
The more active metal replaces the less active metal in the salt (see Appendix Table 9).
For example:
Pb (NO 3) 2 + Zn \u003d Pb + Zn (NO 3) 2,
Hg (NO 3) 2 + Cu \u003d Hg + Cu (NO 3) 2.
2. Salt solutions interact with alkalis, this produces a new base and a new salt.
For example:
CuSO 4 + 2KOH \u003d Cu (OH) 2 + 2K 2 SO 4,
FeCl 3 + 3NaOH \u003d Fe (OH) 3 + 3NaCl.
3. Salts react with solutions of stronger or less volatile acids, this produces a new salt and a new acid.
For example:
a) as a result of the reaction, a weaker acid or a more volatile acid is formed:
Na 2 S + 2HC1 \u003d 2NaCl + H 2 S
b) reactions of salts of strong acids with weaker acids are also possible if a sparingly soluble salt is formed as a result of the reaction:
CuSO 4 + H 2 S \u003d CuS + H 2 SO 4.
4. Salts in solutions enter into exchange reactions with other salts, resulting in two new salts.
For example:
NaС1 + AgNO 3 \u003d AgCl + NaNO 3,
CaCI 2 + Na 2 CO 3 \u003d CaCO 3 + 2NaCl,
CuSO 4 + Na 2 S \u003d CuS + Na 2 SO 4.
It should be remembered that exchange reactions proceed almost to the end if one of the reaction products is released from the reaction sphere in the form of a precipitate, gas, or if water or another weak electrolyte is formed during the reaction.
