| Anoxic: | Basicity | Salt name |
| HCl - hydrochloric (hydrochloric) | monobasic | chloride |
| HBr - hydrobromic | monobasic | bromide |
| HI - hydroiodide | monobasic | iodide |
| HF - hydrofluoric (hydrofluoric) | monobasic | fluoride |
| H 2 S - hydrogen sulfide | dibasic | sulfide |
| Oxygenated: | ||
| HNO 3 - nitrogen | monobasic | nitrate |
| H 2 SO 3 - sulfurous | dibasic | sulfite |
| H 2 SO 4 - sulfuric | dibasic | sulfate |
| H 2 CO 3 - coal | dibasic | carbonate |
| H 2 SiO 3 - silicon | dibasic | silicate |
| H 3 PO 4 - orthophosphoric | tripartite | orthophosphate |
Salts - complex substances that consist of metal atoms and acid residues. This is the most numerous class of inorganic compounds.
Classification. By composition and properties: medium, sour, basic, double, mixed, complex
Medium salts are products of the complete replacement of hydrogen atoms of a polybasic acid with metal atoms.
When dissociated, only metal cations (or NH 4 +) are produced. For example:
Na 2 SO 4 ® 2Na + +SO
CaCl 2 ® Ca 2+ + 2Cl -
Acid salts are products of incomplete substitution of hydrogen atoms of a polybasic acid for metal atoms.
When dissociated, they give metal cations (NH 4 +), hydrogen ions and anions of an acid residue, for example:
NaHCO 3 ® Na + + HCO « H + + CO .
Basic salts are products of incomplete substitution of OH groups - the corresponding base for acidic residues.
Upon dissociation, metal cations, hydroxyl anions and an acid residue are produced.
Zn(OH)Cl ® + + Cl - « Zn 2+ + OH - + Cl - .
double salts contain two metal cations and upon dissociation give two cations and one anion.
KAl(SO 4) 2 ® K + + Al 3+ + 2SO
Complex salts contain complex cations or anions.
Br ® + + Br - « Ag + +2 NH 3 + Br -
Na ® Na + + - « Na + + Ag + + 2 CN -
Genetic relationship between different classes of compounds
EXPERIMENTAL PART
Equipment and utensils: tripod with test tubes, washer, spirit lamp.
Reagents and materials: red phosphorus, zinc oxide, Zn granules, slaked lime powder Ca (OH) 2, 1 mol / dm 3 solutions of NaOH, ZnSO 4, CuSO 4, AlCl 3, FeCl 3, HCl, H 2 SO 4, universal indicator paper, solution phenolphthalein, methyl orange, distilled water.
Work order
1. Pour zinc oxide into two test tubes; add an acid solution (HCl or H 2 SO 4) to one, an alkali solution (NaOH or KOH) to the other and heat slightly on an alcohol lamp.
Observations: Does zinc oxide dissolve in a solution of acid and alkali?
Write Equations
Findings: 1. What type of oxides does ZnO belong to?
2. What properties do amphoteric oxides have?
Preparation and properties of hydroxides
2.1. Dip the tip of the universal indicator strip into an alkali solution (NaOH or KOH). Compare the obtained color of the indicator strip with the standard color scale.
Observations: Record the pH value of the solution.
2.2. Take four test tubes, pour 1 ml of ZnSO 4 solution into the first, СuSO 4 into the second, AlCl 3 into the third, FeCl 3 into the fourth. Add 1 ml of NaOH solution to each tube. Write observations and equations for the reactions that take place.
Observations: Does precipitation occur when alkali is added to a salt solution? Specify the color of the precipitate.
Write Equations ongoing reactions (in molecular and ionic form).
Findings: How can metal hydroxides be obtained?
2.3. Transfer half of the precipitates obtained in experiment 2.2 to other test tubes. On one part of the precipitate, act with a solution of H 2 SO 4 on the other - with a solution of NaOH.
Observations: Does precipitation dissolve when alkali and acid are added to precipitation?
Write Equations ongoing reactions (in molecular and ionic form).
Findings: 1. What type of hydroxides are Zn (OH) 2, Al (OH) 3, Сu (OH) 2, Fe (OH) 3?
2. What properties do amphoteric hydroxides have?
Getting salts.
3.1. Pour 2 ml of CuSO 4 solution into a test tube and lower the cleaned nail into this solution. (The reaction is slow, changes on the surface of the nail appear after 5-10 minutes).
Observations: Are there any changes to the surface of the nail? What is being deposited?
Write an equation for a redox reaction.
Findings: Taking into account a number of stresses of metals, indicate the method for obtaining salts.
3.2. Place one zinc granule in a test tube and add HCl solution.
Observations: Is there any gas evolution?
Write an equation
Findings: Explain this method of obtaining salts?
3.3. Pour a little powder of slaked lime Ca (OH) 2 into a test tube and add a solution of HCl.
Observations: Is there an evolution of gas?
Write an equation the ongoing reaction (in molecular and ionic form).
Conclusion: 1. What type of reaction is the interaction of hydroxide and acid?
2. What substances are the products of this reaction?
3.5. Pour 1 ml of salt solutions into two test tubes: in the first - copper sulfate, in the second - cobalt chloride. Add to both tubes drop by drop sodium hydroxide solution until precipitation is formed. Then add an excess of alkali to both test tubes.
Observations: Indicate the color changes of the precipitates in the reactions.
Write an equation the ongoing reaction (in molecular and ionic form).
Conclusion: 1. As a result of what reactions are basic salts formed?
2. How can basic salts be converted to medium salts?
1. From the listed substances, write out the formulas of salts, bases, acids: Ca (OH) 2, Ca (NO 3) 2, FeCl 3, HCl, H 2 O, ZnS, H 2 SO 4, CuSO 4, KOH
Zn (OH) 2, NH 3, Na 2 CO 3, K 3 PO 4.
2. Specify the oxide formulas corresponding to the listed substances H 2 SO 4, H 3 AsO 3, Bi (OH) 3, H 2 MnO 4, Sn (OH) 2, KOH, H 3 PO 4, H 2 SiO 3, Ge ( OH) 4 .
3. What hydroxides are amphoteric? Write the reaction equations characterizing the amphotericity of aluminum hydroxide and zinc hydroxide.
4. Which of the following compounds will interact in pairs: P 2 O 5 , NaOH, ZnO, AgNO 3 , Na 2 CO 3 , Cr(OH) 3 , H 2 SO 4 . Make equations of possible reactions.
Laboratory work No. 2 (4 hours)
Subject: Qualitative analysis of cations and anions
Target: to master the technique of carrying out qualitative and group reactions to cations and anions.
THEORETICAL PART
The main task of qualitative analysis is to establish chemical composition substances found in a variety of objects (biological materials, drugs, food, objects environment). In this paper, we consider the qualitative analysis of inorganic substances that are electrolytes, i.e., in fact, the qualitative analysis of ions. From the totality of occurring ions, the most important in medical and biological terms were selected: (Fe 3+, Fe 2+, Zn 2+, Ca 2+, Na +, K +, Mg 2+, Cl -, PO, CO, etc. ). Many of these ions are found in various drugs and foods.
In qualitative analysis, not all possible reactions are used, but only those that are accompanied by a distinct analytical effect. The most common analytical effects are: the appearance of a new color, the release of gas, the formation of a precipitate.
There are two fundamentally different approaches to qualitative analysis: fractional and systematic . In a systematic analysis, group reagents are necessarily used to separate the ions present into separate groups, and in some cases into subgroups. To do this, some of the ions are transferred to the composition of insoluble compounds, and some of the ions are left in solution. After separating the precipitate from the solution, they are analyzed separately.
For example, in solution there are A1 3+, Fe 3+ and Ni 2+ ions. If this solution is exposed to an excess of alkali, a precipitate of Fe (OH) 3 and Ni (OH) 2 precipitates, and ions [A1 (OH) 4] - remain in the solution. The precipitate containing hydroxides of iron and nickel, when treated with ammonia, will partially dissolve due to the transition to a solution of 2+. Thus, with the help of two reagents - alkali and ammonia, two solutions were obtained: one contained ions [А1(OH) 4 ] - , the other contained ions 2+ and a precipitate of Fe(OH) 3 . With the help of characteristic reactions, the presence of certain ions in solutions and in the precipitate, which must first be dissolved, is proved.
Systematic analysis is mainly used to detect ions in complex multicomponent mixtures. It is very time-consuming, but its advantage lies in the easy formalization of all actions that fit into a clear scheme (methodology).
For fractional analysis, only characteristic reactions are used. It is obvious that the presence of other ions can significantly distort the results of the reaction (imposition of colors on top of each other, undesirable precipitation, etc.). To avoid this, fractional analysis mainly uses highly specific reactions that give an analytical effect with few ions. For successful reactions, it is very important to maintain certain conditions, in particular, pH. Very often, in fractional analysis, one has to resort to masking, i.e., to the conversion of ions into compounds that are not capable of producing an analytical effect with the selected reagent. For example, dimethylglyoxime is used to detect the nickel ion. A similar analytical effect with this reagent gives the Fe 2+ ion. To detect Ni 2+, the Fe 2+ ion is converted into a stable fluoride complex 4- or oxidized to Fe 3+, for example, with hydrogen peroxide.
Fractional analysis is used to detect ions in simpler mixtures. The analysis time is significantly reduced, however, the experimenter is required to have a deeper knowledge of the patterns of chemical reactions, since it is quite difficult to take into account all possible cases of the mutual influence of ions on the nature of the observed analytical effects in one particular technique.
In analytical practice, the so-called fractional systematic method. With this approach, the minimum number of group reagents is used, which makes it possible to outline the tactics of analysis in in general terms, which is then carried out by the fractional method.
According to the technique of carrying out analytical reactions, reactions are distinguished: sedimentary; microcrystalloscopic; accompanied by the release of gaseous products; carried out on paper; extraction; colored in solutions; flame coloring.
When carrying out sedimentary reactions, the color and nature of the precipitate (crystalline, amorphous) must be noted, if necessary, additional tests are carried out: the precipitate is checked for solubility in strong and weak acids, alkalis and ammonia, and an excess of the reagent. When carrying out reactions accompanied by the evolution of gas, its color and smell are noted. In some cases, additional tests are carried out.
For example, if it is assumed that the evolved gas is carbon monoxide (IV), it is passed through an excess of lime water.
In fractional and systematic analysis, reactions are widely used, during which a new color appears, most often these are complexation reactions or redox reactions.
In some cases, it is convenient to carry out such reactions on paper (drop reactions). Reagents that do not decompose under normal conditions are applied to paper in advance. So, to detect hydrogen sulfide or sulfide ions, paper impregnated with lead nitrate is used [blackening occurs due to the formation of lead (II) sulfide]. Many oxidizing agents are detected using starch iodine paper, i. paper impregnated with solutions of potassium iodide and starch. In most cases, the necessary reagents are applied to the paper during the reaction, for example, alizarin for the A1 3+ ion, cupron for the Cu 2+ ion, etc. To enhance the color, extraction into an organic solvent is sometimes used. Flame color reactions are used for preliminary tests.
acids complex substances are called, the composition of the molecules of which includes hydrogen atoms that can be replaced or exchanged for metal atoms and an acid residue.
According to the presence or absence of oxygen in the molecule, acids are divided into oxygen-containing(H 2 SO 4 sulfuric acid, H 2 SO 3 sulfurous acid, HNO 3 nitric acid, H 3 PO 4 phosphoric acid, H 2 CO 3 carbonic acid, H 2 SiO 3 silicic acid) and anoxic(HF hydrofluoric acid, HCl hydrochloric acid ( hydrochloric acid), HBr hydrobromic acid, HI hydroiodic acid, H 2 S hydrosulfide acid).
Depending on the number of hydrogen atoms in an acid molecule, acids are monobasic (with 1 H atom), dibasic (with 2 H atoms) and tribasic (with 3 H atoms). For example, nitric acid HNO 3 is monobasic, since there is one hydrogen atom in its molecule, sulfuric acid H 2 SO 4 – dibasic, etc.
There are very few inorganic compounds containing four hydrogen atoms that can be replaced by a metal.
The part of an acid molecule without hydrogen is called an acid residue.
Acid Residue they can consist of one atom (-Cl, -Br, -I) - these are simple acid residues, or they can - from a group of atoms (-SO 3, -PO 4, -SiO 3) - these are complex residues.
In aqueous solutions, acid residues are not destroyed during exchange and substitution reactions:
H 2 SO 4 + CuCl 2 → CuSO 4 + 2 HCl
The word anhydride means anhydrous, that is, an acid without water. For example,
H 2 SO 4 - H 2 O → SO 3. Anoxic acids do not have anhydrides.
Acids get their name from the name of the acid-forming element (acid-forming agent) with the addition of the endings “naya” and less often “vaya”: H 2 SO 4 - sulfuric; H 2 SO 3 - coal; H 2 SiO 3 - silicon, etc.
The element can form several oxygen acids. In this case, the indicated endings in the name of the acids will be when the element exhibits the highest valence (in the acid molecule great content oxygen atoms). If the element exhibits a lower valence, the ending in the name of the acid will be “pure”: HNO 3 - nitric, HNO 2 - nitrous.
Acids can be obtained by dissolving anhydrides in water. If the anhydrides are insoluble in water, the acid can be obtained by the action of another stronger acid on the salt of the required acid. This method is typical for both oxygen and anoxic acids. Anoxic acids are also obtained by direct synthesis from hydrogen and non-metal, followed by dissolution of the resulting compound in water:
H 2 + Cl 2 → 2 HCl;
H 2 + S → H 2 S.
Solutions of the resulting gaseous substances HCl and H 2 S and are acids.
Under normal conditions, acids are both liquid and solid.
Chemical properties of acids
Acid solutions act on indicators. All acids (except silicic acid) dissolve well in water. Special substances - indicators allow you to determine the presence of acid.
Indicators are substances of complex structure. They change their color depending on the interaction with different chemicals. In neutral solutions, they have one color, in solutions of bases, another. When interacting with acid, they change their color: the methyl orange indicator turns red, the litmus indicator also turns red.
Interact with bases with the formation of water and salt, which contains an unchanged acid residue (neutralization reaction):
H 2 SO 4 + Ca (OH) 2 → CaSO 4 + 2 H 2 O.
Interact with based oxides with the formation of water and salt (neutralization reaction). The salt contains the acid residue of the acid that was used in the neutralization reaction:
H 3 PO 4 + Fe 2 O 3 → 2 FePO 4 + 3 H 2 O.
interact with metals.
For the interaction of acids with metals, certain conditions must be met:
1. the metal must be sufficiently active with respect to acids (in the series of activity of metals, it must be located before hydrogen). The further to the left a metal is in the activity series, the more intensely it interacts with acids;
2. The acid must be strong enough (that is, capable of donating H + hydrogen ions).
During the course of chemical reactions of an acid with metals, a salt is formed and hydrogen is released (except for the interaction of metals with nitric and concentrated sulfuric acids):
Zn + 2HCl → ZnCl 2 + H 2;
Cu + 4HNO 3 → CuNO 3 + 2 NO 2 + 2 H 2 O.
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Complex substances consisting of hydrogen atoms and an acidic residue are called mineral or inorganic acids. The acid residue is oxides and non-metals combined with hydrogen. The main property of acids is the ability to form salts.
Classification
The basic formula of mineral acids is H n Ac, where Ac is the acid residue. Depending on the composition of the acid residue, two types of acids are distinguished:
- oxygen containing oxygen;
- oxygen-free, consisting only of hydrogen and non-metal.
The main list of inorganic acids according to the type is presented in the table.
|
Type |
Name |
Formula |
|
Oxygen |
||
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nitrogenous |
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dichrome |
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Iodine |
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Silicon - metasilicon and orthosilicon |
H 2 SiO 3 and H 4 SiO 4 |
|
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manganese |
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manganese |
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Metaphosphoric |
||
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Arsenic |
||
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orthophosphoric |
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sulphurous |
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Thiosulphuric |
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Tetrathionic |
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Coal |
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Phosphorous |
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Phosphorous |
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Chlorine |
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Chloride |
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hypochlorous |
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Chrome |
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cyanic |
||
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Anoxic |
Hydrofluoric (hydrofluoric) |
|
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Hydrochloric (hydrochloric) |
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Hydrobromic |
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Hydroiodine |
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Hydrogen sulfide |
||
|
Hydrogen cyanide |
In addition, in accordance with the properties of the acid are classified according to the following criteria:
- solubility: soluble (HNO 3 , HCl) and insoluble (H 2 SiO 3);
- volatility: volatile (H 2 S, HCl) and non-volatile (H 2 SO 4 , H 3 PO 4);
- degree of dissociation: strong (HNO 3) and weak (H 2 CO 3).
Rice. 1. Scheme for the classification of acids.
Traditional and trivial names are used to designate mineral acids. The traditional names correspond to the name of the element that forms the acid with the addition of the morphemic -naya, -ovaya, as well as -pure, -novataya, -novatistaya to indicate the degree of oxidation.
Receipt
The main methods for obtaining acids are presented in the table.
Properties
Most acids are sour-tasting liquids. Tungsten, chromic, boric and several other acids are in a solid state under normal conditions. Some acids (H 2 CO 3, H 2 SO 3, HClO) exist only in the form of an aqueous solution and are weak acids.
Rice. 2. Chromic acid.
Acids are active substances that react:
- with metals:
Ca + 2HCl \u003d CaCl 2 + H 2;
- with oxides:
CaO + 2HCl \u003d CaCl 2 + H 2 O;
- with base:
H 2 SO 4 + 2KOH \u003d K 2 SO 4 + 2H 2 O;
- with salts:
Na 2 CO 3 + 2HCl \u003d 2NaCl + CO 2 + H 2 O.
All reactions are accompanied by the formation of salts.
A qualitative reaction is possible with a change in the color of the indicator:
- litmus turns red;
- methyl orange - in pink;
- phenolphthalein does not change.
Rice. 3. Colors of indicators during acid interaction.
The chemical properties of mineral acids are determined by the ability to dissociate in water with the formation of hydrogen cations and anions of hydrogen residues. Acids that react with water irreversibly (dissociate completely) are called strong acids. These include chlorine, nitrogen, sulfuric and hydrochloric.
What have we learned?
Inorganic acids are formed by hydrogen and an acidic residue, which are non-metal atoms or an oxide. Depending on the nature of the acid residue, acids are classified into anoxic and oxygen-containing. All acids have a sour taste and are able to dissociate in an aqueous medium (decompose into cations and anions). Acids are obtained from simple substances, oxides, salts. When interacting with metals, oxides, bases, salts, acids form salts.
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acids- electrolytes, during the dissociation of which only H + ions are formed from positive ions:
HNO 3 ↔ H + + NO 3 -;
CH 3 COOH ↔ H + +CH 3 COO -.
All acids are classified into inorganic and organic (carboxylic), which also have their own (internal) classifications.
Under normal conditions, a significant amount of inorganic acids exist in a liquid state, some in a solid state (H 3 PO 4, H 3 BO 3).
Organic acids with up to 3 carbon atoms are easily mobile, colorless liquids with a characteristic pungent odor; acids with 4-9 carbon atoms are oily liquids with an unpleasant odor, and acids with a large number of carbon atoms are solids that are insoluble in water.
Chemical formulas of acids
Consider the chemical formulas of acids using the example of several representatives (both inorganic and organic): hydrochloric acid -HCl, sulfuric acid - H 2 SO 4, phosphoric acid - H 3 PO 4, acetic acid - CH 3 COOH and benzoic acid - C 6 H5COOH. The chemical formula shows the qualitative and quantitative composition of the molecule (how many and which atoms are included in a particular compound) Using the chemical formula, you can calculate the molecular weight of acids (Ar (H) \u003d 1 amu, Ar (Cl) \u003d 35.5 a.m.). m.u., Ar(P) = 31 a.m.u., Ar(O) = 16 a.m.u., Ar(S) = 32 a.m.u., Ar(C) = 12 a.u.m.):
Mr(HCl) = Ar(H) + Ar(Cl);
Mr(HCl) = 1 + 35.5 = 36.5.
Mr(H 2 SO 4) = 2×Ar(H) + Ar(S) + 4×Ar(O);
Mr(H 2 SO 4) \u003d 2 × 1 + 32 + 4 × 16 \u003d 2 + 32 + 64 \u003d 98.
Mr(H 3 PO 4) = 3×Ar(H) + Ar(P) + 4×Ar(O);
Mr(H 3 PO 4) \u003d 3 × 1 + 31 + 4 × 16 \u003d 3 + 31 + 64 \u003d 98.
Mr(CH 3 COOH) = 3×Ar(C) + 4×Ar(H) + 2×Ar(O);
Mr(CH 3 COOH) = 3x12 + 4x1 + 2x16 = 36 + 4 + 32 = 72.
Mr(C 6 H 5 COOH) = 7×Ar(C) + 6×Ar(H) + 2×Ar(O);
Mr(C 6 H 5 COOH) = 7x12 + 6x1 + 2x16 = 84 + 6 + 32 = 122.
Structural (graphic) formulas of acids
The structural (graphic) formula of a substance is more visual. It shows how atoms are connected to each other within a molecule. Let us indicate the structural formulas of each of the above compounds:
Rice. 1. Structural formula of hydrochloric acid.
Rice. 2. Structural formula of sulfuric acid.
Rice. 3. Structural formula of phosphoric acid.
Rice. 4. Structural formula of acetic acid.
Rice. 5. Structural formula of benzoic acid.
Ionic formulas
All inorganic acids are electrolytes, i.e. capable of dissociating in an aqueous solution into ions:
HCl ↔ H + + Cl - ;
H 2 SO 4 ↔ 2H + + SO 4 2-;
H 3 PO 4 ↔ 3H + + PO 4 3-.
Examples of problem solving
EXAMPLE 1
| Exercise | With complete combustion 6 g organic matter 8.8 g of carbon monoxide (IV) and 3.6 g of water were formed. Determine the molecular formula of the burned substance if its molar mass is known to be 180 g/mol. |
| Decision | Let's draw up a scheme for the combustion reaction of an organic compound, denoting the number of carbon, hydrogen and oxygen atoms as "x", "y" and "z", respectively: C x H y O z + O z →CO 2 + H 2 O. Let us determine the masses of the elements that make up this substance. The values of relative atomic masses taken from the Periodic Table of D.I. Mendeleev, rounded up to integers: Ar(C) = 12 a.m.u., Ar(H) = 1 a.m.u., Ar(O) = 16 a.m.u. m(C) = n(C)×M(C) = n(CO 2)×M(C) = ×M(C); m(H) = n(H)×M(H) = 2×n(H 2 O)×M(H) = ×M(H); Calculate the molar masses of carbon dioxide and water. As is known, the molar mass of a molecule is equal to the sum of the relative atomic masses of the atoms that make up the molecule (M = Mr): M(CO 2) \u003d Ar (C) + 2 × Ar (O) \u003d 12+ 2 × 16 \u003d 12 + 32 \u003d 44 g / mol; M(H 2 O) \u003d 2 × Ar (H) + Ar (O) \u003d 2 × 1 + 16 \u003d 2 + 16 \u003d 18 g / mol. m(C)=×12=2.4 g; m (H) \u003d 2 × 3.6 / 18 × 1 \u003d 0.4 g. m(O) \u003d m (C x H y O z) - m (C) - m (H) \u003d 6 - 2.4 - 0.4 \u003d 3.2 g. Let's define the chemical formula of the compound: x:y:z = m(C)/Ar(C) : m(H)/Ar(H) : m(O)/Ar(O); x:y:z= 2.4/12:0.4/1:3.2/16; x:y:z= 0.2: 0.4: 0.2 = 1: 2: 1. Means the simplest formula compounds CH 2 O and a molar mass of 30 g / mol. To find the true formula of an organic compound, we find the ratio of the true and obtained molar masses: M substance / M (CH 2 O) \u003d 180 / 30 \u003d 6. This means that the indices of carbon, hydrogen and oxygen atoms should be 6 times higher, i.e. the formula of the substance will look like C 6 H 12 O 6. Is it glucose or fructose. |
| Answer | C6H12O6 |
EXAMPLE 2
| Exercise | Derive the simplest formula of a compound in which the mass fraction of phosphorus is 43.66%, and the mass fraction of oxygen is 56.34%. |
| Decision | The mass fraction of element X in a molecule of composition HX is calculated from following formula:
ω (X) = n × Ar (X) / M (HX) × 100%. Let us denote the number of phosphorus atoms in the molecule as "x", and the number of oxygen atoms as "y" Let us find the corresponding relative atomic masses of the elements phosphorus and oxygen (the values of the relative atomic masses taken from the Periodic Table of D.I. Mendeleev will be rounded up to whole numbers). Ar(P) = 31; Ar(O) = 16. We divide the percentage of elements by the corresponding relative atomic masses. Thus, we will find the relationship between the number of atoms in the molecule of the compound: x:y = ω(P)/Ar(P) : ω(O)/Ar(O); x:y = 43.66/31: 56.34/16; x:y: = 1.4: 3.5 = 1: 2.5 = 2: 5. This means that the simplest formula for the combination of phosphorus and oxygen has the form P 2 O 5. It is phosphorus(V) oxide. |
| Answer | P2O5 |