State budgetary educational institution of higher professional education "Kazan State Medical University" of the Ministry of Health of the Russian Federation MEDICAL-PHARMACEUTICAL COLLEGE History of the development of analytical chemistry Completed by: Davletshina Gulnaz R group
Analytical chemistry is the science of methods for determining the chemical composition of a substance and its structure. However, this definition of CS appears to be exhaustive. The subject of analytical chemistry is the development of analytical methods and their practical implementation, as well as extensive research into the theoretical foundations of analytical methods. This includes the study of the forms of existence of elements and their compounds in various environments and states of aggregation, determination of the composition and stability of coordination compounds, optical, electrochemical and other characteristics of matter, study of the rates of chemical reactions, determination of metrological characteristics of methods, etc. A significant role is given to the search for fundamentally new methods of analysis and the use of modern achievements of science and technology for analytical purposes.
Depending on the task at hand, the properties of the substance being analyzed and other conditions, the composition of substances is expressed differently. The chemical composition of a substance can be characterized by the mass fraction (%) of elements or their oxides or other compounds, as well as the content of individual chemical compounds or phases, isotopes, etc. actually present in the sample. The composition of alloys is usually expressed by the mass fraction (%) of the constituent cements; composition of rocks, ores, minerals, etc., the content of elements in terms of any of their compounds, most often oxides.
The theoretical basis of analytical chemistry is the fundamental laws of natural science, such as the periodic law of D.I. Mendeleev, the laws of conservation of mass of matter and energy, constancy of the composition of matter, effective masses, etc. Analytical chemistry is closely related to physics, inorganic, organic, physical and colloidal chemistry, electrochemistry, chemical thermodynamics, solution theory, metrology, information theory and many other sciences.
Analytical chemistry has important scientific and practical significance. Almost all basic chemical laws have been discovered using the methods of this science. The composition of various materials, products, ores, minerals, lunar soil, distant planets and other celestial bodies was established by methods of analytical chemistry; the discovery of a number of elements of the periodic table was made possible thanks to the use of precise methods of analytical chemistry. The Importance of Analytical Chemistry
Many practical techniques of analytical chemistry and analytical techniques were known in ancient times. This is, first of all, assay art, or assay analysis, which was performed “dry”, that is, without dissolving the sample and using solutions. Using fire assay methods, the purity of precious metals was monitored and their content in ores, alloys, etc. was determined. The fire assay technique reproduced the production process of precious metals in laboratory conditions. These methods of analysis were used in Ancient Egypt and Greece, and they were also known in Kievan Rus. The practical significance of reactions in solution was small at that time. Main stages in the development of analytical chemistry
The development of industry and various industries by the middle of the 17th century. required new methods of analysis and research, since assay analysis could no longer meet the needs of chemical and many other industries. By this time, by the middle of the 17th century. usually refer to the origin of analytical chemistry and the formation of chemistry itself as a science. Determining the composition of ores, minerals and other substances aroused great interest, and chemical analysis became at this time the main method of research in chemical science. R. Boyle () developed general concepts of chemical analysis. He laid the foundations of modern qualitative analysis using the “wet” method, i.e., carrying out reactions in solution, introduced a system of qualitative reactions known at that time and proposed several new ones (for ammonia, chlorine, etc.), used litmus to detect acids and alkalis and made other important discoveries.
M.V. Lomonosov () was the first to systematically use balances in the study of chemical reactions. In 1756, he experimentally established one of the basic laws of nature, the law of conservation of mass of matter, which formed the basis of quantitative analysis and is of great importance for all science. M.V. Lomonosov developed many methods of chemical analysis and research that have not lost their significance to this day (vacuum filtration, gravimetric analysis operations, etc.). M.V. Lomonosov's achievements in the field of analytical chemistry include the creation of the foundations of gas analysis, the use of a microscope to carry out qualitative analysis of the shape of crystals, which later led to the development of microcrystalloscopy analysis, and the design of a refractometer and other instruments. The results of his own research and the experience of a chemist-researcher, analyst and technologist M.V. Lomonosov summarized in the book “The First Foundations of Metallurgy or Ore Mining” (1763), which had a huge influence on the development of analytical chemistry and related fields, as well as metallurgy and ore mining.
The use of precise methods of chemical analysis made it possible to determine the composition of many natural substances and technological processing products and to establish a number of basic laws of chemistry. A.L. Lavoisier () determined the composition of air, water and other substances and developed the oxygen theory of combustion. Based on analytical data, D. Dalton () developed the atomic theory of matter and established the laws of constancy of composition and multiple ratios. J. L. Gay-Lussac () and A. Avogadro () formulated gas laws.
M.V. Severgin () proposed a colorimetric analysis based on the dependence of the color intensity of a solution on the concentration of a substance, J.L. Gay-Lussac developed a titrimetric method of analysis. These methods, together with gravimetric methods, formed the basis of classical analytical chemistry and have retained their importance to the present day. Analytical chemistry, enriched with new methods, continued to develop and improve. At the end of the 18th century. T. E. Lovitz (), developing the ideas of M. V. Lomonosov, created microcrystalscopic analysis - a method for qualitative analysis of salts based on the shape of their crystals.
At the end of the 18th and 19th centuries. through the works of many scientists T. W. Bergman (), L. Z. Tenard (), K. K. Klaus (), and others, a systematic qualitative analysis was created. In accordance with the developed scheme, certain groups of elements were precipitated from the analyzed solution by the action of group reagents, and then individual elements were discovered within these groups. This work was completed by K. R. Fresenius (), who wrote textbooks on qualitative and quantitative analysis and founded the first journal of analytical chemistry (Zeitschrift fur analytische Chemie, currently Fresenius Z. anal. Chem.). At the same time, I. Ya. Berzelius () and J. Liebig () improved and developed methods for analyzing organic compounds for the content of the main elements C, H, N, etc. Titrimetric analysis is progressing noticeably; methods of iodometry, permanganatometry, etc. appear. the discovery is made in R. W. Bunsen () and G. R. Kirchhoff (). They offer spectral analysis, which becomes one of the main methods of analytical chemistry, continuously developing to the present day.
The discovery of the periodic law in 1869 by D. I. Mendeleev () had a huge impact on the development of chemistry and other sciences, and D. I. Mendeleev’s “Fundamentals of Chemistry” became the basis for the study of analytical chemistry. A. M. Butlerov’s creation of the theory of the structure of organic compounds was also of great importance. A significant influence on the formation of analytical chemistry and its teaching was exerted by A. A. Menshutkin’s “Analytical Chemistry”, published in 1871, which went through 16 editions in our country and was translated into German and English. In 1868, on the initiative of D.I. Mendeleev and N.A. Menshutkin, the Russian Chemical Society was established at St. Petersburg University, which began publishing its own journal in 1869. The creation of a scientific chemical society and the publication of the journal had a beneficial effect on the development of domestic chemistry and analytical chemistry in particular.
A special branch of chemistry was developed by N. S. Kurnakov () physicochemical analysis, based on the study of “composition-property” diagrams. The method of physicochemical analysis allows one to determine the composition and properties of compounds formed in complex systems based on the dependence of the properties of the system on its composition without isolating individual compounds in crystalline or other forms.
In 1903, M. S. Tsvet () proposed chromatographic analysis, an effective method for separating compounds with similar properties, based on the use of adsorption and some other properties of the substance. The full merits of this method were only appreciated several decades after its discovery. For the development of partition chromatography, A. Martin and R. Singh were awarded the Nobel Prize in 1954.
Further development of the theory of analytical chemistry is associated with the discovery by N. N. Beketov () of the equilibrium nature of chemical reactions and K. M. Guldberg () and II. Waage () law of mass action. With the advent of S. Arrhenius's theory of electrolytic dissociation in 1887, analytical chemists received a method for effective quantitative control of chemical reactions, and advances in chemical thermodynamics further expanded these possibilities. A significant role in the development of the scientific foundations of analytical chemistry was played by the monograph by V. Ostwald () “Scientific foundations of analytical chemistry in an elementary presentation,” published in 1894. The works of L. V. Pisarzhevsky () and N. A. Shilova () on the electronic theory of redox processes.
Since the 20s of the XX century. Quantitative emission spectral analysis and absorption spectroscopy are beginning to develop intensively. Devices with photoelectric recording of light intensity are being designed. In 1925, J. Heyrovsky () developed polarographic analysis, for which he was awarded the Nobel Prize in 1959. During these same years, chromatographic, radiochemical and many other methods of analysis were developed and improved. Since 1950, the method of atomic absorption spectroscopy proposed by E. Walsh has been rapidly developing.
The development of industry and science required new advanced methods of analysis from analytical chemistry. There was a need for quantitative determinations of impurities at and below levels. It turned out, for example, that the content of so-called forbidden impurities (Cd, Pb, etc.) in rocket technology materials should be no higher than 10~5%, the hafnium content in zirconium, used as a structural material in nuclear technology, should be less than 0, 01%, and in semiconductor technology materials, impurities should be no more than 10%. It is known that the semiconducting properties of germanium were discovered only after samples of this element of high purity were obtained. Zirconium was initially rejected as a structural material in the nuclear industry on the grounds that it itself quickly became radioactive, although according to theoretical calculations this should not have happened. Later it turned out that it was not zirconium that became radioactive, but the usual satellite of zirconium, hafnium, which is found as an impurity in zirconium materials.
Today's analytical chemistry is characterized by many changes: the arsenal of analytical methods is expanding, especially towards physical and biological ones; automation and mathematization of analysis; creation of techniques and means of local, non-destructive, remote, continuous analysis; an approach to solving problems about the forms of existence of components in analyzed samples; the emergence of new opportunities to increase the sensitivity, accuracy and speed of analysis; further expansion of the range of analyzed objects. Computers are now widely used, lasers do a lot of things, laboratory work has appeared; The role of analytical control, especially of objects in our environment, has increased significantly. Interest in methodological problems of analytical chemistry has increased. How to clearly define the subject of this science, what place it occupies in the system of scientific knowledge, whether it is fundamental or applied science, what stimulates its development, these and similar questions have been the subject of many discussions.
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Chemical reaction rate
Research objectives: 1. Define the concept of the rate of a chemical reaction. 2. Experimentally identify factors affecting the rate of a chemical reaction.
2CO (g) + O 2 (g) = 2CO 2 (g) 2HBr (g) ↔H 2 (g) + Br 2 (g) NaOH (r) + HCl (r) = NaCl (r) +H 2 O (l) F (sol) + S (sol) = FeS (sol) Go to the interface CaCO 3 (sol) ↔CaO (sol) + CO 2 (g) CO 2 (g) + C ( tv) = 2CO (g) 4H 2 O (l) + 3Fe (tv) ↔4H 2 (g) + Fe 3 O 4 (tv) Classification of reactions by phase composition
Average rate of a homogeneous reaction The rate of a homogeneous reaction is determined by the change in the concentration of one of the substances per unit time υ = -/+ ΔC Δt mol l s
The average rate of a heterogeneous reaction is determined by the change in the amount of substance that reacted or formed as a result of the reaction per unit time per unit surface Interaction occurs only at the interface between substances S – surface area
Factors influencing the rate of a chemical reaction Nature of the reacting substances Concentration Temperature Catalyst, inhibitor Contact area The reaction occurs when molecules of reacting substances collide, its speed is determined by the number of collisions and their strength (energy)
Nature of reacting substances The reactivity of substances is determined by: the nature of chemical bonds, the speed is greater for substances with ionic and covalent polar bonds (inorganic substances), the rate is lower for substances with covalent low-polar and non-polar bonds (organic substances) υ (Zn + HCl = H 2 + ZnCl 2 ) > υ (Zn + CH 3 COOH = H 2 + Zn(CH3COO) 2 their structure, the speed is greater for metals that give up electrons more easily (with a larger atomic radius), the speed is greater for non-metals that accept electrons more easily (with a smaller atomic radius) υ (2K + 2 H 2 O = H 2 + 2KOH) > υ (2Na + 2 H 2 O = H 2 + 2NaOH)
Jacob van't Hoff (1852-1911) Temperature increases the number of molecular collisions. Van't Hoff's rule (formulated on the basis of an experimental study of reactions) In the temperature range from 0 ° C to 100 ° C, with an increase in temperature for every 10 degrees, the rate of a chemical reaction increases by 2-4 times: Van't Hoff's rule does not have the force of law. Laboratory technology was imperfect, therefore: it turned out that the temperature coefficient was not constant over a significant temperature range; it was impossible to study both very fast reactions (occurring in milliseconds) and very slow (requiring thousands of years) reactions involving large molecules of complex shape (for example , proteins) do not obey the van’t Hoff rule v = v 0 ∆ τ /10 - van’t Hoff temperature coefficient
Concentration For substances to interact, their molecules must collide. The number of collisions is proportional to the number of particles of reacting substances per unit volume, i.e. their molar concentrations. Law of mass action: The rate of an elementary chemical reaction is proportional to the product of the molar concentrations of the reacting substances raised to powers equal to their coefficients: 1867 K. Guldberg and P. Waage formulated the law of mass action a A + b B d D + f F v = k · c (A) a · c (B) b k - reaction rate constant (v = k at c (A) = c (B) = 1 mol/l)
Contact area The rate of a heterogeneous reaction is directly proportional to the contact surface area of the reactants. When grinding and mixing, the contact surface of the reacting substances increases, and the reaction rate increases. The rate of a heterogeneous reaction depends on: a) the rate of supply of reagents to the phase boundary; b) the reaction rate at the interface, which depends on the area of this surface; c) the rate of removal of reaction products from the phase interface.
Profile level At “3” - §13 p.126-139, ex. 1, p. 140. On “4” - §13 p.126-139, exercises 1,2, p.140. On “5” - §13 p.126-139, exercises 4.5, p.140. Basic level At “3” - §12 p.49-55, ex. 5, p. 63. On “4” - §12 p. 49-55, task 1, p.63. On “5” - §12 p. 49-55, task 2, p.63.
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http://www.hemi.nsu.ru/ucheb214.htm http://www.chem.msu.su/rus/teaching/Kinetics-online/welcome.html O.S. Gabrielyan. Chemistry. Grade 11. A basic level of. Textbook for general education institutions, M., Bustard, 2010 I.I.Novoshinsky, N.S.Novoshinskaya. Chemistry. Grade 10. Textbook for educational institutions, M., “ONICS 21st century”; “Peace and Education”, 2004 O.S. Gabrielyan, G.G. Lysova, A.G. Vvedenskaya. Chemistry teacher's handbook. Grade 11. M., Bustard. 2004 K.K.Kurmasheva. Chemistry in tables and diagrams. M., "List New". 2003 N.B. Kovalevskaya. Chemistry in tables and diagrams. M., "Publishing school 2000". 1998 P.A. Orzhekovsky, N.N. Bogdanova, E.Yu. Vasyukova. Chemistry. Collection of tasks. M." Eksmo", 2011 Photos: http://www.google.ru/ Literature:
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General lesson on the topic “Rate of chemical reactions. Chemical balance". Purpose: Generalization of students’ theoretical knowledge about the rate of chemical reactions, factors influencing the speed...
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CLASSIFICATION OF CHEMICAL REACTIONS ACCORDING TO PHASE (AGGREGATE STATE) CHEMICAL REACTIONS HOMOGENEOUS HETEROGENEOUS (reacting substances and reaction products are in the same phase) 2SO2(g) + O2(g)=2SO3(g) HCl(l)+NaOH(l)=NaCl (l)+H2O Feature: they occur throughout the entire volume of the reaction mixture (the reactants and reaction products are in different phases) S(solid)+O2(g)=SO2(g) Zn(solid)+2HCl(l)=ZnCl2( g)+H2(g) Feature: occur at the interface
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RATES OF REACTIONS Rate of homogeneous reaction Rate of heterogeneous reaction A (g) + B (g) = C (g) ∆V = V2-V1 ∆ t = t2-t1 V (hom) = ∆V /(∆ t * V) C = V / V (mol/l) V (gom) = ± ∆С/ ∆ t (mol/l*s) V (het) = ± ∆V /(S*∆ t) (mol/m^2*s)
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Factors influencing the rate of a chemical reaction Concentration A+B=C+D V=k[A]*[B] Nature of reactants Contact surface area temperature catalyst
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Problem 1 At some point in time, the concentration of chlorine in the vessel in which the reaction H2+Cl2=2HCl takes place was equal to 0.06 mol/l. After 5 sec. The chlorine concentration was 0.02 mol/l. What is the average rate of this reaction in the specified period of time? Given C1(Cl2)=0.06 mol/l C2(Cl2)=0.02 mol/l ∆ t = 5 sec V=? Solution H2+Cl2=2HCl V= -(C2 – C1)/ ∆ t = (0.02-0.06)/5 = = 0.008 (mol/l*s) Answer: V = 0.008 (mol/l*s)
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Problem 2 How will the rate of the reaction FeCl3+3KCNS=Fe(CNS)3+3KCl occur in an aqueous solution change when the reacting mixture is diluted by half with water? Given C(ions)< 2 раза V2/V1=? Решение Fe(3+) + 3CNS(-) = Fe(CNS)3 V =k*^3 пусть до разбавления: х = Y = ^3 В результате разбавления концентрация ионов уменьшается: x/2 = y/2 = V2/V1 = k*(x/2)*(y/2)^3 = 16 Ответ: V2/V1 = 16 ^3 – в степени 3
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Problem 3 How will the reaction rate change when the temperature increases from 55 to 100 ‘C, if the temperature coefficient of the rate of this reaction is 2.5? Given γ =2.5 t1= 55 ' t2 = 100 ' Vt2/Vt1=? Solution = 2.5*((100-55)/10) = =25^4.5 = (5/2)^9/9= 43.7 Answer: the reaction rate increases by 43.7 times
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Problem 4 When the temperature increases by 30°C, the rate of some reaction increases by 64 times. What is the temperature coefficient of the rate of this reaction? Given Vt2/Vt1=64 t2 = 30 ’ γ =? Solution = γ^3 64 = γ^3 γ = 4 Answer: The temperature coefficient of the reaction rate is 4.
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Test: consolidation of knowledge 1. To reduce the reaction rate it is necessary: a) increase the concentration of reactants b) introduce a catalyst into the system c) increase the temperature d) lower the temperature 2. The reaction proceeds at the highest speed: a) neutralization b) combustion of sulfur in the air in ) dissolution of magnesium in acid d) reduction of copper oxide with hydrogen 3. Specify a homogeneous reaction. a) CaO+H2O=Ca(OH)2 b) S+O2=SO2 c) 2CO+O2=2CO2 d) MgCO3 MgO+CO2 4. Indicate the heterogeneous reaction. a) 2CO+O2=2CO2 b) H2+Cl2=2HCl c) 2SO2+O2=2SO2 (cat V2O5) d) N2O+H2=N2+H2O 5. Mark which reaction is both homogeneous and catalytic. a) 2SO2+O2=2SO3 (NO2 cat) b) CaO+CO2=CaCO3 c) H2+Cl2=2HCl d) N2+3H2=2NH3 (Fe cat)
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Test: consolidation of knowledge 6. Indicate how the rate of the bimolecular gas reaction 2NO2=N2O4 will change when the concentration of NO2 increases three times. a) will increase by 3 times b) will decrease by 6 times c) will increase by 9 times d) will increase by 6 times 7. Indicate to which process the expression for the law of mass action for the rate of a chemical reaction V=k^x corresponds. a) S+O2=SO2 b) 2H2+O2=2H2O c) 2CO+O2=2CO2 d) N2+O2=2NO 8. Note the rate of which process will not change if the pressure in the reaction vessel is increased (t unchanged). a) 2NO+O2=2NO2 b) H2+Cl2=2HCl c) CaO+H2O=Ca(OH)2 d) N2O4=2NO2 9. Calculate what the temperature coefficient of the reaction rate is, if when the temperature decreases by 40'C its the speed decreased by 81 times.
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Rate of chemical reactions Chemical kinetics studies the rate and mechanisms of chemical reactions
Homogeneous and heterogeneous systems Heterogeneous systems Phase is the totality of all homogeneous parts of the system, identical in composition and in all physical and chemical properties and delimited from other parts of the system by an interface. Homogeneous systems consist of one phase
Rate of chemical reactions (for homogeneous systems) A + B = D + G C 0 = 0.5 mol/l C 1 = 5 mol/l t = 10 s
Rate of chemical reactions (for homogeneous systems) A + B = D + G C 0 = 2 mol/l C 1 = 0.5 mol/l t = 10 s (for heterogeneous systems)
Factors on which the reaction rate depends Nature of the reacting substances Concentration of substances in the system Surface area (for heterogeneous systems) Temperature Availability of catalysts Experiment: influence of concentration Experiment: alkali metals react with water Rubidium and cesium with water
Effect of temperature Van't Hoff's rule When the system is heated by 10 ˚C, the reaction rate increases 2-4 times - Van't Hoff temperature coefficient Jacob Van't Hoff (1852-1911)
Catalysis Jens Jakob Berzelius introduced the term “catalysis” in 1835. A catalyst is a substance that changes the rate of a reaction, participates in the intermediate stages of the reaction, but is not part of the reaction products. 2SO 2 (g.) + O 2 (g.) 2SO 3 (g.) 2) SO 2 (g.) + NO 2 (g.) SO 3 (g.) + NO (g.) 1) 2 NO (g) + O 2 (g) 2NO 2 (g) Wilhelm Ostwald 1909 – Nobel Prize “in recognition of work on catalysis”
The mechanism of decomposition of hydrogen peroxide 2 H 2 O 2 = 2H 2 O + O 2 (1) H 2 O 2 = H + + HO 2 - (2) HO 2 - + H 2 O 2 = H 2 O + O 2 + OH - (3) OH - + H + = H 2 O Watch the experiment “Decomposition of hydrogen peroxide” Go to the topic “catalysis”
Decomposition of H 2 O 2 in the presence of Fe 3+ H 2 O 2 = H + + HO 2 - HO 2 - + Fe 3+ = Fe 2+ + HO 2 HO 2 + Fe 3+ = Fe 2+ + O 2 + H + Fe 2+ + H 2 O 2 = Fe 3+ + OH + OH - OH + H 2 O 2 = H 2 O + HO 2 Fe 2+ + HO 2 = Fe 3+ + HO 2 - OH - + H + = H2O. . . . . . Compare with a mechanism without a catalyst
17 white camels Kai Linderström-Lang (1896-1959) Parable about catalysis + 1 black camel 1/2 1/3 1/9 18 9 6 2 17 + 1 black camel
Terminology Catalysis, catalyst Inhibitor Promoters Catalytic poisons Homogeneous and heterogeneous catalysis Enzymes
Features of enzymatic catalysis High selectivity and specificity of the catalyst Strict requirements for reaction conditions Classification of enzymes Oxyreductases Transferases Hydrolases Lyases Isomerases Ligases (synthetases)
Now to the Unified State Exam questions!
A20-2008-1 The rate of the chemical reaction between a solution of sulfuric acid and iron is not affected by 1) acid concentration 2) grinding of iron 3) reaction temperature 4) increase in pressure
A20-2008-2 To increase the rate of the chemical reaction Mg (solid) + 2 H + = Mg 2+ + H 2 (g), it is necessary to 1) add several pieces of magnesium 2) increase the concentration of hydrogen ions 3) reduce the temperature 4) increase magnesium ion concentration
A20-2008-3 With the highest speed under normal conditions the reaction occurs 1) 2 Ba + O 2 = 2BaO 2) Ba 2+ + CO 3 2- = BaCO 3 ↓ 3) Ba + 2H + = Ba 2+ + H 2 4 ) Ba + S = BaS
A20-2008-4 To increase the rate of the reaction 2CO + O 2 = 2CO 2 + Q it is necessary to 1) increase the concentration of CO 2) reduce the concentration of O 2 3) lower the pressure 4) lower the temperature
A20-2008- 5 To increase the reaction rate Zn (solid) + 2 H + = Zn 2+ + H 2 (g) it is necessary to 1) reduce the concentration of zinc ions 2) increase the concentration of hydrogen ions 3) reduce the temperature 4) increase the concentration zinc ions
1) Zn + HCl (5%p-p) 2) Zn + HCl (10%p-p) 3) Zn + HCl (20%p-p) 4) NaOH (5% p-p) + HCl (5% p-p) With the highest speed at normal conditions the reaction occurs