Calculate the volume produce of hydrogen in water displaceme

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SUMMARY

The forum discussion centers on calculating the volume of hydrogen gas produced via the water displacement method. A sample of 0.0125g of hydrogen was collected at 23.0°C and a pressure of 99.99 kNm^-2, with a water vapor pressure of 2.81 kNm^-2. The calculation using the ideal gas law (PV = nRT) yielded a volume of 158.35 mL, while the provided answer was 0.583 L. The discrepancy is attributed to the molar mass of hydrogen being inaccurately stated as 2 g/mol instead of the more precise 2.02 g/mol, which affects the final volume calculation.

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  • Understanding of the Ideal Gas Law (PV = nRT)
  • Knowledge of significant figures in scientific calculations
  • Familiarity with the concept of water vapor pressure
  • Basic skills in unit conversion (e.g., m³ to mL)
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  • Review the Ideal Gas Law and its applications in gas calculations
  • Learn about the significance of molar mass in stoichiometric calculations
  • Study the effects of significant figures on scientific accuracy
  • Explore the concept of water vapor pressure and its implications in gas collection methods
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Chemistry students, laboratory technicians, and anyone involved in gas collection experiments or stoichiometric calculations will benefit from this discussion.

WeiLoong
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Please post this type of questions in HW section using the template.
0.0125g of hydrogen gas produced was collected using water displacement method at 23.0°C and 99.99kNm^-2. If the pressure of water vapour at the same temperature is 2.81kNm^-2, calculate the volume of hydrogen gas collected

My calculation : PV = nRT
n = No. of moles of H2 = 0.0125/2 = 6.25 x 10^-3 mole
P = 99.99 -2.81 = 97.18 KN/m^2
T = 23degC = 296.15K
R = 8.314J/molK
V = nRT/P = (6.25 x 10^-3 x 8.314 x 296.15)/97180 = 1.5835 x 10^-4 m^3 = 158.35mL

but the answer given is 0.583L any mistakes did i make?
 
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Your answer looks OK to me*. My bet is there is a typo in the answer given - note how 583 digits appear both in both the correct and the given answer.

*Actually it doesn't - if all the data is given with no less than 3 significant digits, molar mass of hydrogen should be accurate as well, not just 2 g/mol, but 2.02 g/mol (or even 2.016 g/mol to avoid rounding errors). That means the volume of 157 mL.
 

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