The following sequence of reaction occurs in commercial production of aqueous nitric acid- 4 NH 3 g -5 O 2 g - 4 NO g - 6 H 2 O l - H -904 kJ -1 2 NO g - O 2 g - 2 NO 2 g - H -112 kJ -2 3 NO 2 g - H 2 O l - 2 HNO 3 aq -NO g - H -140 kJ -3Determine the magnitude of total heat in kJ - mole liberated at constant pressure for the production of exactly 1 mole of aqueous nitric acid by this process

4NH_3(g)+5O_2(g)→ 4NO(g)+6H_2(g) Δ H= 904 kJ ...(1) 2NO(g)+O_2(g)→ 2NO_2 (g) Δ H= 112 kJ ...(2)3NO_2(g)+H_2O(l)→ 2HNO_3(aq)+NO(g) Δ H= 140 kJ ...(3) ...

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Standard XII

Chemistry

Heat of Reaction

The following...

Question

The following sequence of reaction occurs in commercial production of aqueous nitric acid. $4 N H_{3} (g) + 5 O_{2} (g) \to 4 N O (g) + 6 H_{2} O (l) Δ H = - 904 k J . . . (1)$ $2 N O (g) + O_{2} (g) \to 2 N O_{2} (g) Δ H = - 112 k J . . . (2)$ $3 N O_{2} (g) + H_{2} O (l) \to 2 H N O_{3} (a q) + N O (g) Δ H = - 140 k J . . . (3)$
Determine the magnitude of total heat $(i n kJ/mole)$ liberated at constant pressure for the production of exactly 1 mole of aqueous nitric acid by this process

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Solution

$4 N H_{3} (g) + 5 O_{2} (g) \to 4 N O (g) + 6 H_{2} (g) Δ H = - 904 k J . . . (1)$ $2 N O (g) + O_{2} (g) \to 2 N O_{2} (g) Δ H = - 112 k J . . . (2)$ $3 N O_{2} (g) + H_{2} O (l) \to 2 H N O_{3} (a q) + N O (g) Δ H = - 140 k J . . . (3)$
$1 mole of H N O_{3} = \frac{3}{2} moles of N O_{2} \to$
$\frac{3}{2} mole of N O \to \frac{3}{2} mole of N H_{3}$
Heat liberated to produce 1 mole of nitric acid is $\frac{3}{8} \times (Δ H_{1}) + \frac{3}{4} \times (Δ H_{2}) + \frac{1}{2} \times (Δ H_{3})$
$= (\frac{3}{2} \times \frac{1}{4}) (- 904) - (\frac{3}{2} \times \frac{1}{2}) (- 112) - (\frac{3}{2} \times \frac{1}{3}) (- 140)$
$= - 493 {kJ mol}^{- 1}$

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Similar questions

Q. The following sequence of reaction occurs in commercial production of aqueous nitric acid.

4 N H_{3} (g) + 5 O_{2} (g) \to 4 N O (g) + 6 H_{2} O (l) Δ H = - 904 k J . . . (1)

2 N O (g) + O_{2} (g) \to 2 N O_{2} (g) Δ H = - 112 k J . . . (2)

3 N O_{2} (g) + H_{2} O (l) \to 2 H N O_{3} (a q) + N O (g) Δ H = - 140 k J . . . (3)

Determine the magnitude of total heat

(i n kJ/mole)

liberated at constant pressure for the production of exactly 1 mole of aqueous nitric acid by this process

If 1 mole of aqueous nitric acid is formed, calculate total heat released :

{4 N H}_{3 (g)} + {5 O}_{2 (g)} \to {4 N O}_{(g)} + {6 H}_{2} O_{g}

{2 N O}_{g} + O_{2 (g)} \to {2 N O}_{2 (g)}

{3 N O}_{2 (g)} + H_{2} O_{(g)} \to {2 H N O}_{3 (a q)} + {N O}_{(g)}

Δ_{f} H^{⊖}

per mole of

N H_{3} (g)

N O (g)

and

H_{2} O (l)

are

- 11.04

+ 21.60

and

- 68.32 K c a l

, respectively. Calculate the standard heat of reaction at constant pressure and at a constant volume for the reaction:

4 N H_{3} (g) + 5 O_{2} (g) ⟶ 4 N O (g) + 6 H_{2} O (l)

Q. Nitric acid is the most important oxi-acid formed by nitrogen. It is one of the major industrial chemicals and is widely used. Nitric acid is manufactured by the catalytic oxidation of ammonia that is known as Ostwald Process which can be represented by sequence of reactions shown below

4 N H_{3} + 5 O_{2} (g) C a t a l y s t - ---- \to P t / R h 4 N O (g) + 6 H_{2} O (g) . . . (i)

2 N O (g) + O_{2} (g) 1120 K - --- \to 2 N O_{2} (g) . . . (i i)

3 N O_{2} (g) + H_{2} O (l) \to 2 H N O_{3} (a q) + N O (g) . . . (i i i)

The aqueous nitric acid obtained by this method can be concenteated by distillation to

68.5 %

by weight. Further concentration to

98 %

acid can be achieved by dehydration with concentrated sulphuric acid.

If

170 k g

N H_{3}

is heated in excess of oxygen, then the volume of

H_{2} O (l)

produced in

1^{s t}

reaction at STP is (Given that density of water is

1 \frac{g}{m l}

)

Q. Nitric acid can be produced from ammonia in a three steps process:

4 N H_{3} (g) + 5 O_{2} (g) \to 4 N O (g) + 6 H_{2} O (g) (i)

2 N O (g) + O_{2} (g) \to 2 N O_{2} (g) (ii)

3 N O_{2} (g) + H_{2} O \to 2 H N O_{3} (a q) + N O (g) (iii)

Given the percentage yields of (i), (ii) and (iii) reactions as 50 %, 60 % and 80 %. What will be the volume of

N H_{3}

(g) at STP required to produce 1575 g of

H N O_{3}

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