Molar volume. How to find the volume of gas

Gases are the simplest object to study, therefore their properties and reactions between gaseous substances have been studied most fully. To make it easier for us to understand the decision rules calculation tasks,based on the equations of chemical reactions,it is advisable to consider these laws at the very beginning of the systematic study of general chemistry

French scientist J.L. Gay-Lussac laid down the law volumetric relations:

For example, 1 liter of chlorine connects with 1 liter of hydrogen , forming 2 liters of hydrogen chloride ; 2 l sulfur oxide (IV) connect with 1 liter of oxygen, forming 1 liter of sulfur oxide (VI).

This law allowed the Italian scientist assume that molecules of simple gases ( hydrogen, oxygen, nitrogen, chlorine, etc. ) consist of two identical atoms . When hydrogen combines with chlorine, their molecules break down into atoms, and the latter form hydrogen chloride molecules. But since two molecules of hydrogen chloride are formed from one molecule of hydrogen and one molecule of chlorine, the volume of the latter must be equal to the sum of the volumes of the original gases.
Thus, volumetric relations are easily explained if we proceed from the idea of ​​​​the diatomic nature of molecules of simple gases ( H2, Cl2, O2, N2, etc. ) - This, in turn, serves as proof of the diatomic nature of the molecules of these substances.
The study of the properties of gases allowed A. Avogadro to put forward a hypothesis, which was subsequently confirmed by experimental data, and therefore became known as Avogadro’s law:

Avogadro's law implies an important consequence: under the same conditions, 1 mole of any gas occupies the same volume.

This volume can be calculated if the mass is known 1 l gas Under normal conditions conditions, (n.s.) i.e. temperature 273К (О°С) and pressure 101,325 Pa (760 mmHg) , the mass of 1 liter of hydrogen is 0.09 g, its molar mass is 1.008 2 = 2.016 g/mol. Then the volume occupied by 1 mole of hydrogen under normal conditions is equal to 22.4 l

Under the same conditions the mass 1l oxygen 1.492g ; molar 32g/mol . Then the volume of oxygen at (n.s.) is also equal to 22.4 mol.

Hence:

The molar volume of a gas is the ratio of the volume of a substance to the amount of that substance:

Where V m - molar volume of gas (dimensionl/mol ); V is the volume of the system substance;n - the amount of substance in the system. Example entry:V m gas (Well.)=22.4 l/mol.

Based on Avogadro's law, the molar masses of gaseous substances are determined. The greater the mass of gas molecules, the greater the mass of the same volume of gas. Equal volumes of gases under the same conditions contain the same number of molecules, and therefore moles of gases. The ratio of the masses of equal volumes of gases is equal to the ratio of their molar masses:

Where m 1 - mass of a certain volume of the first gas; m 2 — mass of the same volume of the second gas; M 1 And M 2 - molar masses of the first and second gases.

Typically, gas density is determined in relation to the lightest gas - hydrogen (denoted D H2 ). The molar mass of hydrogen is 2g/mol . Therefore we get.

The molecular mass of a substance in the gaseous state is equal to twice its hydrogen density.

Often the density of a gas is determined relative to air (D B ) . Although air is a mixture of gases, they still talk about its average molar mass. It is equal to 29 g/mol. In this case, the molar mass is determined by the expression M = 29D B .

Determination of molecular masses showed that molecules of simple gases consist of two atoms (H2, F2,Cl2, O2 N2) , and molecules of inert gases are made from one atom (He, Ne, Ar, Kr, Xe, Rn). For noble gases, “molecule” and “atom” are equivalent.

Boyle-Mariotte Law: at a constant temperature, the volume of a given amount of gas is inversely proportional to the pressure under which it is located.From here pV = const ,
Where R - pressure, V - volume of gas.

Gay-Lussac's Law: at constant pressure and the change in gas volume is directly proportional to temperature, i.e.
V/T = const,
Where T - temperature on scale TO (kelvin)

Combined gas law of Boyle - Mariotte and Gay-Lussac:
pV/T = const.
This formula is usually used to calculate the volume of a gas under given conditions if its volume under other conditions is known. If a transition is made from normal conditions (or to normal conditions), then this formula is written as follows:
pV/T = p 0 V 0 /T 0 ,
Where R 0 ,V 0 ,T 0 -pressure, gas volume and temperature under normal conditions ( R 0 = 101 325 Pa , T 0 = 273 K V 0 =22.4 l/mol) .

If the mass and quantity of a gas are known, but it is necessary to calculate its volume, or vice versa, use Mendeleev-Clayperon equation:

Where n - amount of gas substance, mol; m — mass, g; M - molar mass of gas, g/iol ; R — universal gas constant. R = 8.31 J/(mol*K)

Before solving problems, you should know the formulas and rules of how to find the volume of gas. We should remember Avogadro's law. And the volume of gas itself can be calculated using several formulas, choosing the appropriate one from them. When selecting the required formula, environmental conditions, in particular temperature and pressure, are of great importance.

Avogadro's law

It says that at the same pressure and the same temperature, the same volumes of different gases will contain the same number of molecules. The number of gas molecules contained in one mole is Avogadro's number. From this law it follows that: 1 Kmol (kilomol) of an ideal gas, any gas, at the same pressure and temperature (760 mm Hg and t = 0*C) always occupies one volume = 22.4136 m3.

How to determine gas volume

• The formula V=n*Vm can most often be found in problems. Here the volume of gas in liters is V, Vm is the molar volume of gas (l/mol), which under normal conditions = 22.4 l/mol, and n is the amount of substance in moles. When the conditions do not have the amount of a substance, but there is a mass of the substance, then we proceed this way: n=m/M. Here M is g/mol (molar mass of the substance), and the mass of the substance in grams is m. In the periodic table it is written under each element, as its atomic mass. Let's add up all the masses and get what we are looking for.
• So, how to calculate the volume of gas. Here is the task: dissolve 10 g of aluminum in hydrochloric acid. Question: how much hydrogen can be released at u.? The reaction equation looks like this: 2Al+6HCl(g)=2AlCl3+3H2. At the very beginning, we find the aluminum (quantity) that reacted according to the formula: n(Al)=m(Al)/M(Al). We take the mass of aluminum (molar) from the periodic table M(Al) = 27 g/mol. Let's substitute: n(Al)=10/27=0.37 mol. From the chemical equation it can be seen that 3 moles of hydrogen are formed when 2 moles of aluminum are dissolved. It is necessary to calculate how much hydrogen will be released from 0.4 moles of aluminum: n(H2)=3*0.37/2=0.56mol. Let's substitute the data into the formula and find the volume of this gas. V=n*Vm=0.56*22.4=12.54l.

Along with mass and volume, chemical calculations often use the amount of a substance proportional to the number of structural units contained in the substance. In each case, it must be indicated which structural units (molecules, atoms, ions, etc.) are meant. The unit of quantity of a substance is the mole.

Mole is the amount of substance containing as many molecules, atoms, ions, electrons or other structural units as there are atoms in 12 g of the 12C carbon isotope.

The number of structural units contained in 1 mole of a substance (Avogadro's constant) is determined with great accuracy; in practical calculations it is taken equal to 6.02 1024 mol -1.

It is not difficult to show that the mass of 1 mole of a substance (molar mass), expressed in grams, is numerically equal to the relative molecular mass of this substance.

Thus, the relative molecular weight (or, for short, molecular weight) of free chlorine C1g is 70.90. Therefore, the molar mass of molecular chlorine is 70.90 g/mol. However, the molar mass of chlorine atoms is half as much (45.45 g/mol), since 1 mole of Cl chlorine molecules contains 2 moles of chlorine atoms.

According to Avogadro's law, equal volumes of any gases taken at the same temperature and the same pressure contain the same number of molecules. In other words, the same number of molecules of any gas occupies the same volume under the same conditions. At the same time, 1 mole of any gas contains the same number of molecules. Consequently, under the same conditions, 1 mole of any gas occupies the same volume. This volume is called the molar volume of the gas and under normal conditions (0°C, pressure 101, 425 kPa) is equal to 22.4 liters.

For example, the statement “the carbon dioxide content of the air is 0.04% (vol.)” means that at a partial pressure of CO 2 equal to the air pressure and at the same temperature, the carbon dioxide contained in the air will take up 0.04% of the total volume occupied by air.

Test task

1. Compare the number of molecules contained in 1 g of NH 4 and in 1 g of N 2. In what case and how many times is the number of molecules greater?

2. Express the mass of one sulfur dioxide molecule in grams.

4. How many molecules are there in 5.00 ml of chlorine under standard conditions?

4. What volume under normal conditions is occupied by 27 10 21 gas molecules?

5. Express the mass of one NO 2 molecule in grams -

6. What is the ratio of the volumes occupied by 1 mole of O2 and 1 mole of Oz (the conditions are the same)?

7. Equal masses of oxygen, hydrogen and methane are taken under the same conditions. Find the ratio of the volumes of gases taken.

8. To the question of how much volume 1 mole of water will occupy under normal conditions, the answer was: 22.4 liters. Is this the correct answer?

9. Express the mass of one HCl molecule in grams.

How many molecules of carbon dioxide are there in 1 liter of air if the volumetric content of CO 2 is 0.04% (normal conditions)?

10. How many moles are contained in 1 m 4 of any gas under normal conditions?

11. Express in grams the mass of one molecule of H 2 O-

12. How many moles of oxygen are in 1 liter of air, if the volume

14. How many moles of nitrogen are in 1 liter of air if its volumetric content is 78% (normal conditions)?

14. Equal masses of oxygen, hydrogen and nitrogen are taken under the same conditions. Find the ratio of the volumes of gases taken.

15. Compare the number of molecules contained in 1 g of NO 2 and in 1 g of N 2. In what case and how many times is the number of molecules greater?

16. How many molecules are contained in 2.00 ml of hydrogen under standard conditions?

17. Express in grams the mass of one molecule of H 2 O-

18. What volume is occupied by 17 10 21 gas molecules under normal conditions?

RATE OF CHEMICAL REACTIONS

When defining the concept chemical reaction rate it is necessary to distinguish between homogeneous and heterogeneous reactions. If a reaction occurs in a homogeneous system, for example, in a solution or in a mixture of gases, then it occurs throughout the entire volume of the system. Speed ​​of homogeneous reaction is the amount of a substance that reacts or is formed as a result of a reaction per unit time per unit volume of the system. Since the ratio of the number of moles of a substance to the volume in which it is distributed is the molar concentration of the substance, the rate of a homogeneous reaction can also be defined as change in concentration per unit time of any of the substances: the initial reagent or the reaction product. To ensure that the calculation result is always positive, regardless of whether it is based on a reagent or a product, the “±” sign is used in the formula:

Depending on the nature of the reaction, time can be expressed not only in seconds, as required by the SI system, but also in minutes or hours. During the reaction, the magnitude of its speed is not constant, but continuously changes: it decreases as the concentrations of the starting substances decrease. The above calculation gives the average value of the reaction rate over a certain time interval Δτ = τ 2 – τ 1. True (instantaneous) speed is defined as the limit to which the ratio Δ tends WITH/ Δτ at Δτ → 0, i.e., the true speed is equal to the derivative of the concentration with respect to time.

For a reaction whose equation contains stoichiometric coefficients that differ from unity, the rate values ​​expressed for different substances are not the same. For example, for the reaction A + 4B = D + 2E, the consumption of substance A is one mole, that of substance B is three moles, and the supply of substance E is two moles. That's why υ (A) = ⅓ υ (B) = υ (D) =½ υ (E) or υ (E) . = ⅔ υ (IN) .

If a reaction occurs between substances located in different phases of a heterogeneous system, then it can only occur at the interface between these phases. For example, the interaction between an acid solution and a piece of metal occurs only on the surface of the metal. Speed ​​of heterogeneous reaction is the amount of a substance that reacts or is formed as a result of a reaction per unit time per unit interface surface:

.

The dependence of the rate of a chemical reaction on the concentration of reactants is expressed by the law of mass action: at a constant temperature, the rate of a chemical reaction is directly proportional to the product of the molar concentrations of the reacting substances raised to powers equal to the coefficients in the formulas of these substances in the reaction equation. Then for the reaction

2A + B → products

the ratio is valid υ ~ · WITH A 2 · WITH B, and to transition to equality a proportionality coefficient is introduced k, called reaction rate constant:

υ = k· WITH A 2 · WITH B = k·[A] 2 ·[B]

(molar concentrations in formulas can be denoted by the letter WITH with the corresponding index and the formula of the substance enclosed in square brackets). The physical meaning of the reaction rate constant is the reaction rate at concentrations of all reactants equal to 1 mol/l. The dimension of the reaction rate constant depends on the number of factors on the right side of the equation and can be c –1 ; s –1 ·(l/mol); s –1 · (l 2 /mol 2), etc., that is, such that in any case, in calculations, the reaction rate is expressed in mol · l –1 · s –1.

For heterogeneous reactions, the equation of the law of mass action includes the concentrations of only those substances that are in the gas phase or in solution. The concentration of a substance in the solid phase is a constant value and is included in the rate constant, for example, for the combustion process of coal C + O 2 = CO 2, the law of mass action is written:

υ = kI·const··= k·,

Where k= kI const.

In systems where one or more substances are gases, the rate of reaction also depends on pressure. For example, when hydrogen interacts with iodine vapor H 2 + I 2 = 2HI, the rate of the chemical reaction will be determined by the expression:

υ = k··.

If you increase the pressure, for example, by 4 times, then the volume occupied by the system will decrease by the same amount, and, consequently, the concentrations of each of the reacting substances will increase by the same amount. The reaction rate in this case will increase 9 times

Dependence of reaction rate on temperature described by van't Hoff's rule: with every 10 degree increase in temperature, the reaction rate increases by 2-4 times. This means that as the temperature increases in an arithmetic progression, the rate of a chemical reaction increases exponentially. The base in the progression formula is temperature coefficient of reaction rateγ, showing how many times the rate of a given reaction increases (or, which is the same thing, the rate constant) with an increase in temperature by 10 degrees. Mathematically, Van't Hoff's rule is expressed by the formulas:

or

where and are the reaction rates, respectively, at the initial t 1 and final t 2 temperatures. Van't Hoff's rule can also be expressed by the following relations:

; ; ; ,

where and are, respectively, the rate and rate constant of the reaction at temperature t; and – the same values ​​at temperature t +10n; n– number of “ten-degree” intervals ( n =(t 2 –t 1)/10), by which the temperature has changed (can be an integer or fractional number, positive or negative).

Test task

1. Find the value of the rate constant for the reaction A + B -> AB, if at concentrations of substances A and B equal to 0.05 and 0.01 mol/l, respectively, the reaction rate is 5 10 -5 mol/(l-min).

2. How many times will the rate of reaction 2A + B -> A2B change if the concentration of substance A is increased by 2 times, and the concentration of substance B is decreased by 2 times?

4. How many times should the concentration of the substance, B 2 in the system 2A 2 (g) + B 2 (g) = 2A 2 B (g), be increased so that when the concentration of substance A decreases by 4 times, the rate of the direct reaction does not change ?

4. Some time after the start of the reaction 3A+B->2C+D, the concentrations of substances were: [A] =0.04 mol/l; [B] = 0.01 mol/l; [C] =0.008 mol/l. What are the initial concentrations of substances A and B?

5. In the system CO + C1 2 = COC1 2, the concentration was increased from 0.04 to 0.12 mol/l, and the chlorine concentration was increased from 0.02 to 0.06 mol/l. How many times did the rate of the forward reaction increase?

6. The reaction between substances A and B is expressed by the equation: A + 2B → C. The initial concentrations are: [A] 0 = 0.04 mol/l, [B] o = 0.05 mol/l. The reaction rate constant is 0.4. Find the initial reaction rate and the reaction rate after some time, when the concentration of substance A decreases by 0.01 mol/l.

7. How will the rate of the reaction 2CO + O2 = 2CO2, occurring in a closed vessel, change if the pressure is doubled?

8. Calculate how many times the reaction rate will increase if the temperature of the system is increased from 20 °C to 100 °C, taking the value of the temperature coefficient of the reaction rate equal to 4.

9. How will the reaction rate 2NO(r.) + 0 2 (g.) → 2N02(r.) change if the pressure in the system is increased by 4 times;

10. How will the reaction rate 2NO(r.) + 0 2 (g.) → 2N02(r.) change if the volume of the system is reduced by 4 times?

11. How will the rate of the reaction 2NO(r.) + 0 2 (g.) → 2N02(r.) change if the concentration of NO is increased by 4 times?

12. What is the temperature coefficient of the reaction rate if, with an increase in temperature by 40 degrees, the reaction rate

increases by 15.6 times?

14. . Find the value of the rate constant for the reaction A + B -> AB, if at concentrations of substances A and B equal to 0.07 and 0.09 mol/l, respectively, the reaction rate is 2.7 10 -5 mol/(l-min).

14. The reaction between substances A and B is expressed by the equation: A + 2B → C. The initial concentrations are: [A] 0 = 0.01 mol/l, [B] o = 0.04 mol/l. The reaction rate constant is 0.5. Find the initial reaction rate and the reaction rate after some time, when the concentration of substance A decreases by 0.01 mol/l.

15. How will the reaction rate 2NO(r.) + 0 2 (g.) → 2N02(r.) change if the pressure in the system is doubled;

16. In the system CO + C1 2 = COC1 2, the concentration was increased from 0.05 to 0.1 mol/l, and the chlorine concentration was increased from 0.04 to 0.06 mol/l. How many times did the rate of the forward reaction increase?

17. Calculate how many times the reaction rate will increase if the temperature of the system is increased from 20 °C to 80 °C, taking the value of the temperature coefficient of the reaction rate equal to 2.

18. Calculate how many times the reaction rate will increase if the temperature of the system is increased from 40 °C to 90 °C, taking the value of the temperature coefficient of the reaction rate equal to 4.

CHEMICAL BOND. FORMATION AND STRUCTURE OF MOLECULES

1.What types of chemical bonds do you know? Give an example of the formation of an ionic bond using the valence bond method.

2. What chemical bond is called covalent? What is characteristic of the covalent type of bond?

4. What properties are characterized by a covalent bond? Show this with specific examples.

4. What type of chemical bond is in H2 molecules; Cl 2 HC1?

5.What is the nature of the bonds in molecules? NCI 4 CS 2, CO 2? Indicate for each of them the direction of displacement of the common electron pair.

6. What chemical bond is called ionic? What is characteristic of the ionic type of bond?

7. What type of bond is in the NaCl, N 2, Cl 2 molecules?

8. Draw all possible ways of overlapping the s-orbital with the p-orbital;. Indicate the direction of communication in this case.

9. Explain the donor-acceptor mechanism of covalent bonds using the example of the formation of phosphonium ion [PH 4 ]+.

10. In CO molecules, C0 2, is the bond polar or nonpolar? Explain. Describe hydrogen bonding.

11. Why are some molecules that have polar bonds generally nonpolar?

12.Covalent or ionic type of bond is typical for the following compounds: Nal, S0 2, KF? Why is an ionic bond an extreme case of a covalent bond?

14. What is a metal bond? How is it different from a covalent bond? What properties of metals does it determine?

14. What is the nature of the bonds between atoms in molecules; KHF 2, H 2 0, HNO ?

15. How can we explain the high bond strength between atoms in the nitrogen molecule N2 and the significantly lower strength in the phosphorus molecule P4?

16 . What kind of bond is called a hydrogen bond? Why is the formation of hydrogen bonds not typical for H2S and HC1 molecules, unlike H2O and HF?

17. What bond is called ionic? Does an ionic bond have the properties of saturation and directionality? Why is it an extreme case of covalent bonding?

18. What type of bond is in the molecules NaCl, N 2, Cl 2?

: V = n*Vm, where V is the volume of gas (l), n is the amount of substance (mol), Vm is the molar volume of gas (l/mol), at normal (norm) is a standard value and is equal to 22, 4 l/mol. It happens that the condition does not contain the quantity of a substance, but there is a mass of a certain substance, then we do this: n = m/M, where m is the mass of the substance (g), M is the molar mass of the substance (g/mol). We find the molar mass using the table D.I. Mendeleev: under each element is its atomic mass, add up all the masses and get what we need. But such tasks are quite rare, usually present in the tasks. The solution to such problems changes slightly. Let's look at an example.

What volume of hydrogen will be released under normal conditions if aluminum weighing 10.8 g is dissolved in excess hydrochloric acid.

If we are dealing with a gas system, then the following formula holds: q(x) = V(x)/V, where q(x)(phi) is the fraction of the component, V(x) is the volume of the component (l), V – system volume (l). To find the volume of a component, we obtain the formula: V(x) = q(x)*V. And if you need to find the volume of the system, then: V = V(x)/q(x).

note

There are other formulas for finding volume, but if you need to find the volume of a gas, only the formulas given in this article are suitable.

Sources:

• "Chemistry Manual", G.P. Khomchenko, 2005.
• how to find the amount of work
• Find the volume of hydrogen during the electrolysis of a ZnSO4 solution

An ideal gas is one in which the interaction between molecules is negligible. In addition to pressure, the state of a gas is characterized by temperature and volume. The relationships between these parameters are reflected in the gas laws.

Instructions

The pressure of a gas is directly proportional to its temperature, the amount of substance, and inversely proportional to the volume of the vessel occupied by the gas. The proportionality coefficient is the universal gas constant R, approximately equal to 8.314. It is measured in joules divided by moles and by .

This position forms the mathematical dependence P=νRT/V, where ν is the amount of substance (mol), R=8.314 is the universal gas constant (J/mol K), T is the gas temperature, V is the volume. Pressure is expressed in . It can be expressed by and , with 1 atm = 101.325 kPa.

The considered dependence is a consequence of the Mendeleev-Clapeyron equation PV=(m/M) RT. Here m is the mass of the gas (g), M is its molar mass (g/mol), and the fraction m/M gives the total amount of substance ν, or the number of moles. The Mendeleev-Clapeyron equation is valid for all gases that can be considered. This is the physical gas law.

Lesson 1.

Topic: Amount of substance. Mole

Chemistry is the science of substances. How to measure substances? In what units? In the molecules that make up substances, but this is very difficult to do. In grams, kilograms or milligrams, but this is how mass is measured. What if we combine the mass that is measured on a scale and the number of molecules of a substance, is this possible?

a) H-hydrogen

A n = 1a.u.m.

1a.u.m = 1.66*10 -24 g

Let's take 1g of hydrogen and count the number of hydrogen atoms in this mass (have students do this using a calculator).

N n = 1g / (1.66*10 -24) g = 6.02*10 23

b) O-oxygen

A o = 16 a.u.m = 16 * 1.67 * 10 -24 g

N o = 16 g / (16 * 1.66 * 10 -24) g = 6.02 * 10 23

c) C-carbon

A c = 12a.u.m = 12*1.67*10 -24 g

N c = 12g / (12* 1.66*10 -24) g = 6.02*10 23

Let us conclude: if we take a mass of a substance that is equal to the atomic mass in size, but taken in grams, then there will always be (for any substance) 6.02 * 10 23 atoms of this substance.

H 2 O - water

18 g / (18 * 1.66 * 10 -24) g = 6.02 * 10 23 water molecules, etc.

N a = 6.02*10 23 - Avogadro’s number or constant.

A mole is the amount of a substance that contains 6.02 * 10 23 molecules, atoms or ions, i.e. structural units.

There are moles of molecules, moles of atoms, moles of ions.

n is the number of moles (the number of moles is often denoted),
N is the number of atoms or molecules,
N a = Avogadro's constant.

Kmol = 10 3 mol, mmol = 10 -3 mol.

Display a portrait of Amedeo Avogadro on a multimedia installation and briefly talk about him, or instruct the student to prepare a short report on the life of the scientist.

Lesson 2.

Topic: “Molar mass of a substance”

What is the mass of 1 mole of a substance? (Students can often draw the conclusion themselves.)

The mass of one mole of a substance is equal to its molecular mass, but expressed in grams. The mass of one mole of a substance is called molar mass and is denoted by M.

Formulas:

M - molar mass,
n - number of moles,
m is the mass of the substance.

The mass of a mole is measured in g/mol, the mass of a kmole is measured in kg/kmol, the mass of a mmol is measured in mg/mol.

Fill out the table (tables are distributed).

Lesson 3.

Topic: Molar volume of gases

Let's solve the problem. Determine the volume of water, the mass of which under normal conditions is 180 g.

Given:

Those. We calculate the volume of liquid and solid bodies through density.

But, when calculating the volume of gases, it is not necessary to know the density. Why?

The Italian scientist Avogadro determined that equal volumes of different gases under the same conditions (pressure, temperature) contain the same number of molecules - this statement is called Avogadro's law.

Those. if, under equal conditions, V(H 2) =V(O 2), then n(H 2) =n(O 2), and vice versa, if, under equal conditions, n(H 2) =n(O 2), then the volumes of these gases will be the same. And a mole of a substance always contains the same number of molecules 6.02 * 10 23.

We conclude - under the same conditions, moles of gases should occupy the same volume.

Under normal conditions (t=0, P=101.3 kPa. or 760 mm Hg.), moles of any gases occupy the same volume. This volume is called molar.

V m =22.4 l/mol

1 kmol occupies a volume of -22.4 m 3 /kmol, 1 mmol occupies a volume of -22.4 ml/mmol.

Example 1.(To be solved on the board):