In life, we are faced with different chemical reactions. Some of them, like the rusting of iron, can go on for several years. Others, such as the fermentation of sugar into alcohol, take several weeks. Firewood in the stove burns out in a couple of hours, and gasoline in the engine burns out in a split second.

To reduce equipment costs, chemical plants increase the rate of reactions. And some processes, such as food spoilage, metal corrosion, need to be slowed down.

The rate of a chemical reaction can be expressed as change in the amount of matter (n, modulo) per unit time (t) - compare the speed of a moving body in physics as a change in coordinates per unit time: υ = Δx/Δt . So that the rate does not depend on the volume of the vessel in which the reaction takes place, we divide the expression by the volume of reacting substances (v), i.e., we obtain change in the amount of a substance per unit time per unit volume, or change in the concentration of one of the substances per unit time:

n 2 − n 1
υ = –––––––––– = –––––––– = Δс/Δt (1)
(t 2 − t 1) v Δt v

where c = n / v is the concentration of the substance,

Δ (pronounced "delta") is the generally accepted designation for a change in magnitude.

If substances have different coefficients in the equation, the reaction rate for each of them, calculated by this formula, will be different. For example, 2 moles of sulfur dioxide reacted completely with 1 mole of oxygen in 10 seconds in 1 liter:

2SO 2 + O 2 \u003d 2SO 3

The oxygen velocity will be: υ \u003d 1: (10 1) \u003d 0.1 mol / l s

Sour gas speed: υ \u003d 2: (10 1) \u003d 0.2 mol / l s- this does not need to be memorized and spoken in the exam, an example is given in order not to get confused if this question arises.

The rate of heterogeneous reactions (involving solids) is often expressed per unit area of ​​contacting surfaces:

Δn
υ = –––––– (2)
Δt S

Reactions are called heterogeneous when the reactants are in different phases:

• a solid with another solid, liquid or gas,
• two immiscible liquids
• gas liquid.

Homogeneous reactions occur between substances in the same phase:

• between well-miscible liquids,
• gases,
• substances in solutions.

Conditions affecting the rate of chemical reactions

1) The reaction rate depends on the nature of the reactants. Simply put, different substances react at different rates. For example, zinc reacts violently with hydrochloric acid, while iron reacts rather slowly.

2) The reaction rate is greater, the higher concentration substances. With a highly dilute acid, the zinc will take significantly longer to react.

3) The reaction rate increases significantly with increasing temperature. For example, in order to burn fuel, it is necessary to set it on fire, that is, to increase the temperature. For many reactions, an increase in temperature by 10°C is accompanied by an increase in the rate by a factor of 2–4.

4) Speed heterogeneous reactions increases with increasing surfaces of reactants. Solids for this are usually crushed. For example, in order for iron and sulfur powders to react when heated, iron must be in the form of small sawdust.

Note that formula (1) is implied in this case! Formula (2) expresses the speed per unit area, therefore it cannot depend on the area.

5) The reaction rate depends on the presence of catalysts or inhibitors.

Catalysts Substances that speed up chemical reactions but are not themselves consumed. An example is the rapid decomposition of hydrogen peroxide with the addition of a catalyst - manganese (IV) oxide:

2H 2 O 2 \u003d 2H 2 O + O 2

Manganese (IV) oxide remains on the bottom and can be reused.

Inhibitors- substances that slow down the reaction. For example, to extend the life of pipes and batteries, corrosion inhibitors are added to the water heating system. In automobiles, corrosion inhibitors are added to the brake fluid.

A few more examples.

The rate of a chemical reaction

The rate of a chemical reaction- change in the amount of one of the reacting substances per unit of time in a unit of reaction space. It is a key concept of chemical kinetics. The rate of a chemical reaction is always positive, therefore, if it is determined by the initial substance (the concentration of which decreases during the reaction), then the resulting value is multiplied by −1.

For example for a reaction:

the expression for speed will look like this:

. The rate of a chemical reaction at each point in time is proportional to the concentrations of the reactants, raised to powers equal to their stoichiometric coefficients.

For elementary reactions, the exponent at the concentration value of each substance is often equal to its stoichiometric coefficient; for complex reactions, this rule is not observed. In addition to concentration, the following factors influence the rate of a chemical reaction:

• the nature of the reactants,
• the presence of a catalyst
• temperature (van't Hoff rule),
• pressure,
• the surface area of ​​the reactants.

If we consider the simplest chemical reaction A + B → C, then we notice that instant the rate of a chemical reaction is not constant.

Literature

• Kubasov A. A. Chemical kinetics and catalysis.
• Prigogine I., Defey R. Chemical thermodynamics. Novosibirsk: Nauka, 1966. 510 p.
• Yablonsky G. S., Bykov V. I., Gorban A. N., Kinetic models of catalytic reactions, Novosibirsk: Nauka (Siberian Branch), 1983.- 255 p.

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See what the "Rate of a chemical reaction" is in other dictionaries:

CHEMICAL REACTION RATE- the basic concept of chemical kinetics. For simple homogeneous reactions, the rate of a chemical reaction is measured by the change in the number of moles of the reacted substance (at a constant volume of the system) or by the change in the concentration of any of the starting substances ... Big Encyclopedic Dictionary

CHEMICAL REACTION RATE- the basic concept of chem. kinetics, expressing the ratio of the amount of the reacted substance (in moles) to the length of time during which the interaction occurred. Since the concentrations of the reactants change during the interaction, the rate is usually ... Great Polytechnic Encyclopedia

chemical reaction rate- a value that characterizes the intensity of a chemical reaction. The rate of formation of a reaction product is the amount of this product as a result of a reaction per unit time per unit volume (if the reaction is homogeneous) or per ... ...

chemical reaction rate- the basic concept of chemical kinetics. For simple homogeneous reactions, the rate of a chemical reaction is measured by a change in the number of moles of the reacted substance (at a constant volume of the system) or by a change in the concentration of any of the starting substances ... encyclopedic Dictionary

The rate of a chemical reaction- a value characterizing the intensity of a chemical reaction (See Chemical Reactions). The rate of formation of a reaction product is the amount of this product resulting from the reaction per unit time in unit volume (if ... ...

CHEMICAL REACTION RATE- main the concept of chem. kinetics. For simple homogeneous reactions S. x. R. measured by a change in the number of moles of reacted in va (at a constant volume of the system) or by a change in the concentration of any of the initial in in or reaction products (if the volume of the system ...

CHEMICAL REACTION MECHANISM- For complex reactions consisting of several. stages (simple, or elementary reactions), the mechanism is a set of stages, as a result of which the initial ones in va are converted into products. Intermediate in you in these reactions can act as molecules, ... ... Natural science. encyclopedic Dictionary

Nucleophilic substitution reactions- (English nucleophilic substitution reaction) substitution reactions in which the attack is carried out by a nucleophile reagent carrying an unshared electron pair. The leaving group in nucleophilic substitution reactions is called a nucleofug. All ... Wikipedia

Chemical reactions- the transformation of some substances into others, different from the original in chemical composition or structure. The total number of atoms of each given element, as well as the chemical elements themselves that make up substances, remain in R. x. unchanged; this R. x ... Great Soviet Encyclopedia

drawing speed- linear speed of metal movement at the exit from the die, m/s. On modern drawing machines, the drawing speed reaches 50-80 m/s. However, even during wire drawing, the speed, as a rule, does not exceed 30–40 m/s. At… … Encyclopedic Dictionary of Metallurgy

Basic concepts studied:

The rate of chemical reactions

Molar concentration

Kinetics

Homogeneous and heterogeneous reactions

Factors affecting the rate of chemical reactions

catalyst, inhibitor

Catalysis

Reversible and irreversible reactions

Chemical equilibrium

Chemical reactions are reactions in which other substances are obtained from one substance (new substances are formed from the original substances). Some chemical reactions take place in fractions of a second (an explosion), while others take minutes, days, years, decades, etc.

For example: the burning reaction of gunpowder occurs instantly with ignition and explosion, and the reaction of darkening of silver or rusting of iron (corrosion) proceeds so slowly that it is possible to follow its result only after a long time.

To characterize the speed of a chemical reaction, the concept of the rate of a chemical reaction is used - υ.

The rate of a chemical reaction is the change in the concentration of one of the reactants of the reaction per unit time.

The formula for calculating the rate of a chemical reaction is:

υ =	from 2 to 1	=	∆ s
t2 – t1	∆t

c 1 - molar concentration of the substance at the initial time t 1

c 2 - molar concentration of the substance at the initial time t 2

since the rate of a chemical reaction is characterized by a change in the molar concentration of the reacting substances (starting substances), then t 2 > t 1, and c 2 > c 1 (the concentration of the starting substances decreases as the reaction proceeds).

Molar concentration (s) is the amount of substance per unit volume. The unit of measurement of molar concentration is [mol/l].

The branch of chemistry that studies the rate of chemical reactions is called chemical kinetics. Knowing its laws, a person can control chemical processes, set them a certain speed.

When calculating the rate of a chemical reaction, it must be remembered that reactions are divided into homogeneous and heterogeneous.

Homogeneous reactions- reactions that occur in the same environment (i.e., the reactants are in the same state of aggregation; for example: gas + gas, liquid + liquid).

heterogeneous reactions- these are reactions occurring between substances in an inhomogeneous medium (there is a phase interface, i.e. the reacting substances are in a different state of aggregation; for example: gas + liquid, liquid + solid).

The above formula for calculating the rate of a chemical reaction is valid only for homogeneous reactions. If the reaction is heterogeneous, then it can only take place on the interface between the reactants.

For a heterogeneous reaction, the rate is calculated by the formula:

∆ν - change in the amount of substance

S is the area of ​​the interface

∆ t is the time interval during which the reaction took place

The rate of chemical reactions depends on various factors: the nature of the reactants, the concentration of substances, temperature, catalysts or inhibitors.

Dependence of the reaction rate on the nature of the reactants.

Let's analyze this dependence of the reaction rate for example: we put into two test tubes, which contain the same amount of hydrochloric acid solution (HCl), metal granules of the same area: in the first test tube, an iron (Fe) granule, and in the second - a magnesium (Mg) granule. As a result of observations, according to the rate of hydrogen evolution (H 2), it can be seen that magnesium reacts with hydrochloric acid at the highest rate than iron. The rate of this chemical reaction is influenced by the nature of the metal (i.e. magnesium is a more reactive metal than iron and therefore reacts more vigorously with acid).

Dependence of the rate of chemical reactions on the concentration of reactants.

The higher the concentration of the reacting (initial) substance, the faster the reaction proceeds. Conversely, the lower the concentration of the reactant, the slower the reaction.

For example: we will pour a concentrated solution of hydrochloric acid (HCl) into one test tube, and a dilute solution of hydrochloric acid into another. We put in both test tubes a granule of zinc (Zn). We observe, by the rate of hydrogen evolution, that the reaction will go faster in the first test tube, because the concentration of hydrochloric acid in it is greater than in the second test tube.

To determine the dependence of the rate of a chemical reaction, law of action of (acting) masses : the rate of a chemical reaction is directly proportional to the product of the concentrations of the reactants, taken in powers that are equal to their coefficients.

For example, for a reaction proceeding according to the scheme: nA + mB → D , the rate of a chemical reaction is determined by the formula:

υ ch.r. = k C (A) n C (B) m , where

υ x.r - chemical reaction rate

C(A)- BUT

C (V) - molar concentration of a substance AT

n and m - their coefficients

k- chemical reaction rate constant (reference value).

The law of mass action does not apply to substances that are in a solid state, because their concentration is constant (due to the fact that they react only on the surface, which remains unchanged).

For example: for a reaction 2 Cu + O 2 \u003d 2 CuO the reaction rate is determined by the formula:

υ ch.r. \u003d k C (O 2)

PROBLEM: The rate constant of the reaction 2A + B = D is 0.005. calculate the reaction rate at a molar concentration of substance A \u003d 0.6 mol / l, substance B \u003d 0.8 mol / l.

The dependence of the rate of a chemical reaction on temperature.

This dependence is determined van't Hoff rule (1884): with an increase in temperature for every 10 ° C, the rate of a chemical reaction increases on average 2-4 times.

So, the interaction of hydrogen (H 2) and oxygen (O 2) almost does not occur at room temperature, so the rate of this chemical reaction is so low. But at a temperature of 500 C about this reaction proceeds in 50 minutes, and at a temperature of 700 C about - almost instantly.

The formula for calculating the rate of a chemical reaction according to the van't Hoff rule:

where: υ t 1 and υ t 2 are the rates of chemical reactions at t 2 and t 1

γ is the temperature coefficient, which shows how many times the reaction rate increases with an increase in temperature by 10 ° C.

Change in reaction rate:

2. Substitute the data from the problem statement into the formula:

The dependence of the reaction rate on special substances - catalysts and inhibitors.

Catalyst A substance that increases the rate of a chemical reaction but does not itself participate in it.

Inhibitor A substance that slows down a chemical reaction but does not take part in it.

Example: in a test tube with a solution of 3% hydrogen peroxide (H 2 O 2), which is heated, let's add a smoldering splinter - it will not light up, because the reaction rate of decomposition of hydrogen peroxide into water (H 2 O) and oxygen (O 2) is very low, and the resulting oxygen is not enough to carry out a qualitative reaction to oxygen (combustion maintenance). Now let's put a little black powder of manganese (IV) oxide (MnO 2) into the test tube and we will see that the rapid evolution of gas (oxygen) bubbles has begun, and the smoldering torch introduced into the test tube flares up brightly. MnO 2 is a catalyst for this reaction, it accelerated the reaction rate, but did not participate in it itself (this can be proved by weighing the catalyst before and after the reaction - its mass will not change).

Some chemical reactions occur almost instantly (explosion of an oxygen-hydrogen mixture, ion exchange reactions in an aqueous solution), the second - quickly (combustion of substances, the interaction of zinc with acid), and others - slowly (rusting of iron, decay of organic residues). So slow reactions are known that a person simply cannot notice them. For example, the transformation of granite into sand and clay takes place over thousands of years.

In other words, chemical reactions can proceed with different speed.

But what is speed reaction? What is the exact definition of this quantity and, most importantly, its mathematical expression?

The rate of a reaction is the change in the amount of a substance in one unit of time in one unit of volume. Mathematically, this expression is written as:

Where n 1 and n 2- the amount of substance (mol) at time t 1 and t 2, respectively, in a system with a volume V.

Which plus or minus sign (±) will stand before the expression of speed depends on whether we are looking at a change in the amount of which substance - a product or a reactant.

Obviously, in the course of the reaction, the consumption of reagents occurs, that is, their number decreases, therefore, for the reagents, the expression (n 2 - n 1) always has a value less than zero. Since the speed cannot be a negative value, in this case, a minus sign must be placed before the expression.

If we are looking at the change in the amount of the product, and not the reactant, then the minus sign is not required before the expression for calculating the rate, since the expression (n 2 - n 1) in this case is always positive, because the amount of product as a result of the reaction can only increase.

The ratio of the amount of substance n to the volume in which this amount of substance is, called the molar concentration With:

Thus, using the concept of molar concentration and its mathematical expression, we can write another way to determine the reaction rate:

The reaction rate is the change in the molar concentration of a substance as a result of a chemical reaction in one unit of time:

Factors affecting the reaction rate

It is often extremely important to know what determines the rate of a particular reaction and how to influence it. For example, the oil refining industry literally fights for every additional half a percent of the product per unit of time. After all, given the huge amount of oil processed, even half a percent flows into a large annual financial profit. In some cases, it is extremely important to slow down any reaction, in particular, the corrosion of metals.

So what does the rate of a reaction depend on? It depends, oddly enough, on many different parameters.

In order to understand this issue, first of all, let's imagine what happens as a result of a chemical reaction, for example:

The equation written above reflects the process in which the molecules of substances A and B, colliding with each other, form molecules of substances C and D.

That is, undoubtedly, in order for the reaction to take place, at least a collision of the molecules of the starting substances is necessary. Obviously, if we increase the number of molecules per unit volume, the number of collisions will increase in the same way as the frequency of your collisions with passengers in a crowded bus will increase compared to a half-empty one.

In other words, the reaction rate increases with increasing concentration of the reactants.

In the case when one or several of the reactants are gases, the reaction rate increases with increasing pressure, since the pressure of a gas is always directly proportional to the concentration of its constituent molecules.

However, the collision of particles is a necessary but not sufficient condition for the reaction to proceed. The fact is that, according to calculations, the number of collisions of the molecules of the reacting substances at their reasonable concentration is so large that all reactions must proceed in an instant. However, this does not happen in practice. What's the matter?

The fact is that not every collision of reactant molecules will necessarily be effective. Many collisions are elastic - molecules bounce off each other like balls. In order for the reaction to take place, the molecules must have sufficient kinetic energy. The minimum energy that the molecules of the reactants must have in order for the reaction to take place is called the activation energy and is denoted as E a. In a system consisting of a large number of molecules, there is an energy distribution of molecules, some of them have low energy, some have high and medium energy. Of all these molecules, only a small fraction of the molecules have an energy greater than the activation energy.

As is known from the course of physics, temperature is actually a measure of the kinetic energy of the particles that make up the substance. That is, the faster the particles that make up the substance move, the higher its temperature. Thus, obviously, by raising the temperature, we essentially increase the kinetic energy of the molecules, as a result of which the proportion of molecules with energies exceeding E a increases, and their collision will lead to a chemical reaction.

The fact of the positive effect of temperature on the reaction rate was empirically established as early as the 19th century by the Dutch chemist Van't Hoff. Based on his research, he formulated a rule that still bears his name, and it sounds like this:

The rate of any chemical reaction increases by 2-4 times with an increase in temperature by 10 degrees.

The mathematical representation of this rule is written as:

where V 2 and V 1 is the speed at temperature t 2 and t 1, respectively, and γ is the temperature coefficient of the reaction, the value of which most often lies in the range from 2 to 4.

Often the rate of many reactions can be increased by using catalysts.

Catalysts are substances that speed up a reaction without being consumed.

But how do catalysts manage to increase the rate of a reaction?

Recall the activation energy E a . Molecules with energies less than the activation energy cannot interact with each other in the absence of a catalyst. Catalysts change the path along which the reaction proceeds, similar to how an experienced guide will pave the route of the expedition not directly through the mountain, but with the help of bypass paths, as a result of which even those satellites that did not have enough energy to climb the mountain will be able to move to another her side.

Despite the fact that the catalyst is not consumed during the reaction, nevertheless it takes an active part in it, forming intermediate compounds with reagents, but by the end of the reaction it returns to its original state.

In addition to the above factors affecting the reaction rate, if there is an interface between the reacting substances (heterogeneous reaction), the reaction rate will also depend on the contact area of ​​the reactants. For example, imagine a granule of metallic aluminum that has been dropped into a test tube containing an aqueous solution of hydrochloric acid. Aluminum is an active metal that can react with non-oxidizing acids. With hydrochloric acid, the reaction equation is as follows:

2Al + 6HCl → 2AlCl 3 + 3H 2

Aluminum is a solid, which means it only reacts with hydrochloric acid on its surface. Obviously, if we increase the surface area by first rolling the aluminum granule into foil, we thereby provide a greater number of aluminum atoms available for reaction with the acid. As a result, the reaction rate will increase. Similarly, an increase in the surface of a solid can be achieved by grinding it into a powder.

Also, the rate of a heterogeneous reaction, in which a solid reacts with a gaseous or liquid, is often positively affected by stirring, which is due to the fact that as a result of stirring, the accumulating molecules of the reaction products are removed from the reaction zone and a new portion of the reagent molecules is “brought up”.

The last thing to note is also the huge influence on the rate of the reaction and the nature of the reagents. For example, the lower the alkali metal is in the periodic table, the faster it reacts with water, fluorine reacts most quickly with hydrogen gas among all halogens, etc.

In summary, the reaction rate depends on the following factors:

1) the concentration of reagents: the higher, the greater the reaction rate.

2) temperature: with increasing temperature, the rate of any reaction increases.

3) the contact area of ​​the reactants: the larger the contact area of ​​the reactants, the higher the reaction rate.

4) stirring, if the reaction occurs between a solid and a liquid or gas, stirring can accelerate it.

Tasks with comments and solutions

Example 23. The increase in the rate of the reaction, the equation of which 2CO + O 2 = 2CO 2, contributes

1) increase in CO concentration

2) decrease in the concentration of O 2

3) pressure drop

4) lowering the temperature

It is known that the rate of a chemical reaction depends on the following factors:

The nature of the reacting substances (ceteris paribus, more active substances react faster);

The concentration of reactants (the higher the concentration, the higher the reaction rate);

Temperatures (an increase in temperature leads to an acceleration of reactions);

The presence of a catalyst (the catalyst speeds up the process);

Pressure (for reactions involving gases, an increase in pressure is equivalent to an increase in concentration, so the rate of reactions increases with increasing pressure);

The degree of grinding of solids (the greater the degree of grinding, the greater the surface area of ​​contact of the solid reagents, and the higher the reaction rate).

Considering these factors, we analyze the proposed answers:

1) an increase in the concentration of CO (initial substance) will indeed lead to an increase in the rate of a chemical reaction;

2) a decrease in the concentration of O 2 will lead not to an increase, but to a decrease in the reaction rate;

3) a decrease in pressure is essentially the same as a decrease in the concentration of reagents, therefore, the reaction rate will also decrease;

4) a decrease in temperature always leads to a decrease in the rate of a chemical reaction.

Example 24. The rate of reaction between iron and hydrochloric acid is increased by

1) adding an inhibitor

2) lowering the temperature

3) pressure increase

4) increase in HCl concentration

First of all, we write the reaction equation:

Let's analyze the proposed answers. It is known that the addition of an inhibitor reduces the reaction rate, and a decrease in temperature also has a similar effect. A change in pressure does not affect the rate of this reaction (because there are no gaseous substances among the reagents). Therefore, to increase the reaction rate, the concentration of one of the reactants, namely hydrochloric acid, should be increased.

Example 25. The rate of the reaction between acetic acid and ethanol is not affected

1) catalyst

2) temperature

3) concentration of starting substances

4) pressure

Acetic acid and ethanol are liquids. Therefore, the change in pressure does not affect the rate of reaction between these substances, because this factor affects only reactions involving gaseous substances.

Example 26. Reacts with hydrogen at the highest rate

4) carbon

Carbon and sulfur are low-active non-metals. When heated, their activity increases markedly; at high temperatures, gaseous hydrogen will interact with solid sulfur (sulfur melting point 444 ° C) and solid carbon. The chemical activity of halogens is much greater than other non-metals (ceteris paribus). The most active of the halogens is fluorine. As you know, even such stable substances as water and fiberglass burn in a fluorine atmosphere. Indeed, hydrogen and chlorine interact either when heated or in bright light, while fluorine and hydrogen explode under any conditions (even at very low temperatures).

Tasks for independent work

79. Hydrochloric acid reacts most rapidly with

2) sodium hydroxide (solution)

3) iron

4) iron(II) carbonate

80. The reaction rate increases with

1) increasing the concentration of CO

2) lowering the temperature

3) pressure increase

4) rise in temperature

5) grinding reagents

81.

A. The interaction of nitrogen with hydrogen is faster at high pressure.

B. The reaction rate depends on the temperature.

1) only A is true

2) only B is true

3) both statements are true

4) both judgments are wrong

82. interact with the highest rate at room temperature

83. Speed ​​reaction will increase at

1) increase in the concentration of sulfur dioxide

2) rise in temperature

3) lowering the temperature

4) increase in pressure

5) decrease in oxygen concentration

84. The rate of chemical reaction between sulfuric acid solution and iron is not affected

1) increase in acid concentration

2) change in vessel volume

3) increase in reaction temperature

4) pressure increase

5) iron grinding

85. The reaction between water and

1) sodium

2) calcium

3) magnesium

86. interact with the fastest

87. The rate of a reaction whose scheme increases with

1) increasing the concentration of iron ions

2) a decrease in the concentration of iron ions

3) lowering the temperature

4) increasing the concentration of acid

5) grinding iron

88. Are the following statements about the rate of a chemical reaction correct?

A. The rate of interaction of zinc with oxygen depends on the pressure of oxygen in the system.

B. With an increase in temperature by 10 ° C, the rate of most reactions increases by 2-4 times.

1) only A is true

2) true, only B

3) both statements are true

4) both judgments are wrong

89. The rate of reaction is not affected by the change

1) concentration of hydrochloric acid

2) pressure

3) concentration of sodium chloride

4) concentration of sodium sulfite

5) temperature

90. Under normal conditions, the reaction proceeds at the highest rate, the equation / scheme of which

91. Are the following statements about the rate of a chemical reaction correct?

A. The interaction of oxygen with zinc proceeds at a higher rate than with copper.

B. The reaction rate in solution depends on the concentration of the reactants.

1) only A is true

2) only B is true

3) both statements are true

4) both judgments are wrong

92. Interact with the lowest rate at room temperature

1) copper sulfate (solution) and sodium hydroxide (solution)

2) sodium and water

3) oxygen and zinc

4) sulfuric acid (solution) and calcium carbonate (tv)

93. Are the following statements about the rate of a chemical reaction correct?

A. The interaction of zinc with hydrochloric acid proceeds at a higher rate than with orthophosphoric acid of the same concentration.

B. The rate of a reaction in a solution depends on the volume of the vessel in which the reaction is carried out.

1) only A is true

2) only B is true

3) both statements are true

4) both judgments are wrong