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Organic Chemistry – Some Basic Principles And Techniques

Question
CBSEENCH11007648
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How will you estimate phosphorus in an organic compound?

Solution
A known mass of the organic substance is heated with fuming nitric acid in Carius tube. Phosphorus present in the compound is oxidised to phosphoric acid (H3PO4). It is treated with magnesia mixture (MgCl2 + NH4Cl + NH4OH) when a precipitate of magnesium ammonium phosphate (MgNH4PO4) is obtained. It is ignited to obtain magnesium pyrophosphate (Mg2P2O7). From the mass of magnesium pyrophosphate, the percentage of phosphorus can be calculated.
Organic compound         +     Fuming HNO3  rightwards arrow with Heat on top          H3PO4
(Containing phosphorus)                                          Phosphoric acid
space space straight H subscript 3 PO subscript 4 space rightwards arrow with left parenthesis Mg to the power of 2 plus end exponent space plus space NH subscript 4 superscript plus right parenthesis on top space stack MgNH subscript 4 PO subscript 4 6 straight H subscript 2 straight O with Magnesium space ammonium space phosphate below space space space space space space space space space space space space space space space rightwards arrow from 1173 space straight K to Ignite of space stack Mg subscript 2 straight P subscript 2 straight O subscript 7 with Magnesium space pyrosphosphate below
Calculations:
Mass of the organic compound taken = Wg
         Mass space of space Mg subscript 2 straight P subscript 2 straight O subscript 7 space formed space space equals space ag
      Now space space space space space space space space space space space space space space space space Mg subscript 2 straight P subscript 2 straight O subscript 7 space identical to space space 2 straight P 2 cross times 24 plus 2 cross times 31 plus 7 cross times 16 space space space space space space space 2 cross times 31 equals space 222 space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals 62
Now 222 g of Mg2P2O7 contains phosphorus
                                            = 62 g
therefore space space straight a space straight g space of space Mg subscript 2 straight P subscript 2 straight O subscript 7 space would space contain space phosphorus space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space 62 over 222 cross times space straight a space straight g Hence space percentage space of space phosphorus space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals fraction numerator 62 space cross times straight a space cross times 100 over denominator 222 space cross times space straight W end fraction

Some More Questions From Organic Chemistry – Some Basic Principles and Techniques Chapter

How many chain isomers are possible for pentane?

Which characteristic is common to different isomers of a compound?

 

Name three alkanes which do not show chain isomerism.

Name the types of structural isomerism shown by alkanes.

Name the four main types of structural isomerism. 

Write the three possible open chains of five carbon atoms

What types of structural isomerism is shown by the following pairs of organic compounds ?

Write the tautomer of acetaldehyde and write its IUPAC name.

Draw the structure of the tautomer of phenol and write its IUPAC name.

Define ring - chain isomerism. Given one example.?

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