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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Chemistry
Chapter
States of Matter

NTA Abhyas 2020 · Chemistry · States of Matter

A sample of hydrogen gas was collected over water at 21 ° C and 685...

A sample of hydrogen gas was collected over water at 21°C21 ° C and 685 mm Hg. The volume of the container was 7.80 L. Calculate the mass of H2(g){H}_{2} ( g ) collected (vapour pressure of water = 18.6 mm Hg at 21°C21 ° C )

Options

  1. A0.283 g
  2. B0.570 g
  3. C0.589 g
  4. D7.14 g

Correct answer

B. 0.570 g

Step-by-step solution

The volume of H2{H}_{2} at STP
V2=P1V1T1×T2P2{V}_{2} = \dfrac{{P}_{1}{V}_{1}}{{T}_{1}} \times \dfrac{{T}_{2}}{{P}_{2}}
Here vapour pressure of H2{H}_{2} at 21°C21 ° C
= 685 mm – 18.6 mm = 666.4 mm
So V2=666.4mmHg×7.80L×273K294K×760mm=6.38L{V}_{2} = \dfrac{666.4\text{mm}\text{Hg} \times \text{7}\text{.80}\text{L} \times \text{273}\text{K}}{294\text{K} \times \text{760}\text{mm}} = 6.38\text{L}
At STP 22.4LH2weight=2g\text{22}\text{.4}\text{L}{H}_{2} \text{weight}\text{=}\text{2}\text{g}
So, at STP 6.38LH2weigh=2g\times6.38L22.4L=0.570g\text{6}\text{.38}\text{L}{H}_{2} \text{weigh}\text{=}\dfrac{\text{2}\text{g}\text{\times}\text{6}\text{.38}\text{L}}{\text{22}\text{.4}\text{L}} \text{=}\text{0}\text{.570}\text{g}
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