Skip to main content

Application of Gay-Lussac’s Law of Combining Volumes

Gay Lussac’s of combining volumes states that gases react in simple ratio with one another and to volumes of the products provided that temperature and pressure remain constant. In this article, you will understand how to apply this law in calculation by studying the following examples below: 1.     2H 2 + O 2 → H 2 O In the reaction above, what volume of hydrogen would be left over when 300cm 3 of oxygen and hydrogen are exploded in a sealed tube?   1cm 3 of oxygen = 2cm 3 of hydrogen 300cm 3 of oxygen = 2 x 300 = 600cm 3 Volume of left over = 1000 – 600 = 400cm 3 2.     Calculate the volume of carbon (II) oxide required to react with 40cm 3 of oxygen. 2CO + O 2 → 2CO 2 1cm 3 of oxygen = 2cm 3 of CO 40cm 3 of oxygen = 2 x 40 = 80cm 3 3.     Calculate the volume of residual gases that would be produced when 100cm 3 of sulphur (IV) oxide reacts with 20cm 3 of oxygen    2SO 2 + O 2 → 2SO 3 1cm 3 of O 2 = 2cm 3 20cm 3 of O 2 = 2 x 20 = 40cm 3

Mole, Molar mass and Molar Volume

                                                                                                            


 Mole

A mole of any substance is the amount of that substance which contains many elementary particles as the number of atoms in 12 grams of carbon -12. These elementary particles can be atoms, ions, electrons, molecules etc. A mole is a unit used in measuring the amount of particles.

  The number of particles in one mole of any substance is equal to 6.02 x 1023. This number is also known as Avogadro’s number.

     Molar Mass

This is the mass of one mole of any substance expressed in grams. It is also the formula mass which is the sum of all atomic masses of all atoms in a compound expressed in grams.

Example question 1

Calculate the molar mass of the following substances

i)                               sodium chloride

ii)                             chlorine

iii)                           Oxygen

(Na=23, Cl =35.5, O=16

 Solution

 

 

Sodium chloride

The relative atomic mass of Na is 23 and that of Chlorine is 35.5

The formula of sodium chloride is NaCl,

23 + 35.5 = 58.5

1 mole of sodium chloride contains 58.5g.

                Chlorine

Chlorine is a diatomic molecule, Cl2

The relative atomic mass of chlorine is 35.5

Cl2 = 2 x35.5 = 71

1 mole of Chlorine contains 71g

   Oxygen

Oxygen is also a diatomic molecule and its relative atomic mass is 16

O2= 2 x 16 =32

1mole of oxygen contains 32g

   Molar Volume

Molar volume is the volume occupied by one mole of any gas at standard temperature and pressure (s.t.p). It is equal to 22.4dm3 or 22400cm3

22.4dm3 = 6.02 x1023 = 1mole of any gas at s.t.p.

Example question 2

In a laboratory preparation of hydrogen, 5.4g of potassium reacts with water as follows:

                      2K(s) + 2H2O(l) ------ 2KOH(aq) + H2(g)

Calculate:

a)   The mass of water which reacts with 5.4g of potassium

b)   The volume of hydrogen produced at s.t.p

c)    The mass of hydroxide ions produced

(K=39, H=1, O=16, molar volume of gas =22.4dm3, Avogadro’s number = 6.02x1023)

            Solution

2K + 2H2O --------- 2KOH +  H2

From the equation,

a.         2moles of K = 2moles of H2O

             2 x 39g of K = 2 x18g of H2O

            78g of K = 36g of H2O

           5.4g of K = 36/78 x 5.4

            = 2.49g

b.     2 moles of K = 1 mole of H2

78g of K = 22.4dm3 or 22400cm3

5.4g of K = 22400/78 x 5.4

= 1550 cm3

 

c.     2K + 2H2O ------- K+ + 2OH-  + H2

2 moles of K = 2moles of OH- ions

78g of K = 2 x 6.02x1023

5.4g of K = 1.204x1023/78x5.4

= 8.34x1022 of OH-

 

 

 

 

 

Comments

Popular posts from this blog

Application of Gay-Lussac’s Law of Combining Volumes

Gay Lussac’s of combining volumes states that gases react in simple ratio with one another and to volumes of the products provided that temperature and pressure remain constant. In this article, you will understand how to apply this law in calculation by studying the following examples below: 1.     2H 2 + O 2 → H 2 O In the reaction above, what volume of hydrogen would be left over when 300cm 3 of oxygen and hydrogen are exploded in a sealed tube?   1cm 3 of oxygen = 2cm 3 of hydrogen 300cm 3 of oxygen = 2 x 300 = 600cm 3 Volume of left over = 1000 – 600 = 400cm 3 2.     Calculate the volume of carbon (II) oxide required to react with 40cm 3 of oxygen. 2CO + O 2 → 2CO 2 1cm 3 of oxygen = 2cm 3 of CO 40cm 3 of oxygen = 2 x 40 = 80cm 3 3.     Calculate the volume of residual gases that would be produced when 100cm 3 of sulphur (IV) oxide reacts with 20cm 3 of oxygen    2SO 2 + O 2 → 2SO 3 1cm 3 of O 2 = 2cm 3 20cm 3 of O 2 = 2 x 20 = 40cm 3

Qualitative Analysis of inorganic Compound

  This is a type analysis which involves the identification of the ions ( cation and anion) in a given inorganic substance. Thus, Qualitative analysis deals with the identification of the compound. To effectively identify the ions, it is necessary to be able to observe the presence of any chemical reaction which is normally recognized by ·         Colour change ·         Evolution of gas ·         Precipitation      Colour Change : colour change is associated with transition metal ions. The major cause of the colour in transition metal ions is electronic transition within the d-block level. The colour of light which show, is the colour of light which is reflected by the ion. This change of transition metal ions is common when they form a bond with water or ammonia. It is important to note that zinc does not form coloured ion, this is because zinc has completely filled the d orbital, but zinc is yellow when hot and white when cold. Evolution of gas : This is identified by

Qualitative Analysis of Ammonium Trioxocarbonate (IV)

              Ammonium trioxocarbonate(IV) is an electrovalent compound just like any other ammonium salts. As an electrovalent compound, it has NH + (ammonium ion) as the cation and CO 3 2- (trioxocarbonate IV ion or radical) as the anion.                          (NH 4 ) 2 CO 3   -------    2NH 4 + + CO 3 2- Ammonium trioxocarbonate IV is a white crystal salt and it is very soluble in water like all other ammonium salts. It decomposes on heating to produce ammonium, water and carbon (IV)oxide.                      (NH 4 + ) 2 CO 3   ----------   2NH 3(g) + H 2 O (I) + CO 2(g)          Test for the Cation in Ammonium Trioxocarbonate IV To test the unknown sample, put the sample into a boiling tube, add a base or alkali into the boiling tube and heat gently.   Note: All ammonium salts liberate ammonia when heated with base or alkali.         (NH 4 ) 2 CO 3(s) + 2NaOH (aq) ----------   Na 2 CO 3 (aq) + H 2 O (l) + 2NH 3(g) Test the gas liberated with damp li