Question

The decompostion NH3 gas on a heated tungsten surface gave the following results :

Initial pressure (mm) 65 105 y 185

Half-life (sec) 290 x 670 820

Calculate approximately the values of x and y.

• A. x = 410 secy = 115 mm
• B. x = 467 secy = 150 mm
• C. x = 490 secy = 120 mm
• D. x = 430 secy = 105 mm

Answer 1

Answer: (B)

x = 467 secy = 150 mm

Answer 2

$\text{Initial pressure } \text{65} \text{105} \text{ y} \text{185} \text{Half life } \text{290} \text{ x} \text{670} \text{820}$Initial pressure of gas a Initial moles of gas in above question.

Half life a Initial pressure

So, it must be zero order reaction

$t_{1/2} = \frac{C_{o}}{2k} = \frac{P_{o}}{2k}290 = \frac{65}{2k} \Rightarrow k = \frac{65}{2 \times 290} = 0.112mmofHg/\sec$

$x = \frac{105 \times 2 \times 290}{2 \times 65} = 468\sec{}670 = \frac{y \times 2 \times 290}{2 \times 64} \Rightarrow y = 150mmofHg$