JEE Main · 2021 · 27 Aug 2021 · Shift 1 · Practical and Analytical Chemistry

The number of moles of CuO, that will be utilized in Dumas method for estimating nitrogen in a sample of 57.5 g of

N, N

-dimethylaminopentane is ______

\times 1 0^{- 2}

. (Nearest integer).

Answer: 1125

Solution

N, N

-dimethylaminopentane,

C_{7} H_{17} N

, has molar mass

115 g mo l^{- 1}

, so

57.5 g

0.5

mol. In the Dumas method

CuO

furnishes the oxygen that burns the compound:

C_{7} H_{17} N + 22.5 CuO \to 7 C O_{2} + 8.5 H_{2} O + \frac{1}{2} N_{2} + 22.5 Cu

, since oxidising

7

carbons needs

14

oxygen atoms and

17

hydrogens need

8.5

, a total of

22.5

per molecule. For

0.5

mol this is

0.5 \times 22.5 = 11.25

mol, that is

1125 \times 1 0^{- 2}

mol.

JEE Main · 2021 · 27 Aug 2021 · Shift 1 · Integer answer

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