Organic Chemistry – Some Basic Principles And Techniques

Step 1: 
First, calculate the pressure of nitrogen as follows: 
\( P_{N_{2}} \ = \ P_{Total} \ – \ P_{H_{2}O}\)

= 725 – 25 = 700 mm  

Now calculate the weight of nitrogen produced by using the PV =nRT formula as follows: 

Weight of nitrogen =  $\frac{\mathrm{pVM}}{\mathrm{RT}}$
where p is pressure= 700 mm 
V is the volume of nitrogen = 40 mL 
M is the molecular mass of N₂ = 28 
R = 0.0821 Latm K^-1 mol^-1 
T =300 K 

Step 2: 

On substituting, 
Weight of nitrogen = $\frac{700\times 40\times 28}{760\times 1000\times 300\times 0.0821}$
= 0.042 g 

The amount of organic compound is 0.25. Calculate the percentage of nitrogen as follows:

% of nitrogen =$\frac{0.042}{0.25}\times 100=16.8$ $\%$

Ammonium phosphomolybdate is
\(\left({NH_{4}}\right)_3PO_{4}.12MoO_{3}\)
Oxidation state of Mo
\(\underset{\left({{NH}_{4}^{{+}}}\right)}{{3}\left({{+}{1}}\right)}{+}\underset{{PO}_{4}^{{3}{-}}}{\left({{-}{3}}\right)}{+}\underset{Mo}{12x}{+}\underset{Oxygen}{{36}\left({{-}{2}}\right)}{=}{0}\)
Calculation gives x = +6