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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
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WAEC 2023 Exams Preparatory Class on the Analysis of Lead Trioxonitrate V

  


  The analysis of lead trioxonitrate V can be done using different tests to help identify the ions present in the compound.

   This tutorial class will be based on one of the several methods of testing for the ions in lead trioxonitrate V salt.

 Procedure:

  Put some lead trioxonitrate V salt sample into a test tube and add about 10 cm3 of distilled water, then shake very well to dissolve. Divide the solution into five portions.

1.     To the first portion, add dilute sodium hydroxide solution in drops then excess. A white precipitate which is soluble in excess dilute sodium hydroxide indicates that zinc ions, aluminium ions or lead ions might be present in the solution.

 

2.      Add aqueous ammonia in drops then in excess to the second portion. A white precipitate is formed which is insoluble in excess aqueous ammonia indicating that zinc ions are absent and aluminium ions or lead ions might be present.

 

3.     To the third portion, add dilute hydrochloric acid and warm gently. A white precipitate which is soluble when it is hot and insoluble when it is cold indicates that lead ions are likely to present.

 

4.     To the fourth portion, add potassium iodide solution. A yellow precipitate confirms the presence of lead ions in the solution.

 

5.     To the fifth portion, add concentrated tetraoxosulphate (VI), H2SO4, acid and add copper turning then warm gently. The liberation of a gas with a strong unpleasant smell confirms the presence of trioxonitrate V ion (NO3-).

 

Example Question

Q is a sample of an inorganic compound carry out the following tests on Q and record your observation and inference.

 

Test

Observation

Inference

1

Q +distilled water and divide into five portions

 

Coloured ions are absent. K+, Na+, NH+ or NO3- likely present

2

To the first portion from (1)above, add dilute NaOH solution in drops then in excess

A white precipitate which is soluble in excess

 

3

To the second portion from (1) above, add aqueous ammonia in drops then in excess

 

Zn2+ absent. Pb2+ or Al3+ is likely to be present.

4

To the third portion from (1) above, add dilute HCl acid and warm gently

 

Pb2+  likely present

5

To the fourth portion from (1) above, add potassium iodide solution

A yellow precipitate formed

 

6

To the fifth portion from (1) above, add H2SO4 and copper turning then warm gently.

 

NO3- confirmed

 

 

 

 

 

 

 

 

 

 

 

 

 



Answer

 

 

Test

Observation

Inference

1

Q +distilled water and divide into five portions

Soluble and gives a clear solution

Coloured ions are absent. K+, Na+, NH+ or NO3- likely present

2

To the first portion from (1)above, add dilute NaOH solution in drops then in excess

A white precipitate which is soluble in excess

Zn2+, Pb2+ or Al3+

Likely present.

3

To the second portion from (1) above, add aqueous ammonia in drops then in excess

A white precipitate which is insoluble in excess

Zn2+ absent. Pb2+ or Al3+   is like to be present.

4

To the third portion from (1) above, add dilute HCl acid and warm gently

A white precipitate which soluble when hot and insoluble when cold

Pb2+  likely present

5

To the fourth portion from (1) above, add potassium iodide solution

A yellow precipitate formed

Pb2+  confirmed

6

To the fifth portion from (1) above, add H2SO4 and copper turning then warm gently.

A brownish gas with a strong unpleasant smell liberated.

NO2  liberated

NO3- confirmed

 

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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
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