56 Experiment 8 Ideal Gas Law: Est mation of Molar Mass of Magnesium QUESTIONS P
ID: 510144 • Letter: 5
Question
56 Experiment 8 Ideal Gas Law: Est mation of Molar Mass of Magnesium QUESTIONS PRE LAB A 0.0500 g sample of magnesium is reacted with 25 mLof 30 M sulfuric acid as described in the experimen tal section. The resulting hydrogen as is collected over water and is found to have a volume of 51.0 temperature is 25 "Cand the atmospheric pressure is 760.00 m Hg. The column of water height inside the cylinder is found to be 24.0 mm. 1. what is the height of the water column after converting to an equivalent height of mercury in mm? 2. What is the pressure of the hydrogen gas in the column in mm Hg? 3. What is the pressure in question 2 converted to atmospheres? 4. What is the number of moles of hydrogen gas in the sample? 5. What is the number of moles of metal in the sample? 6. What is the calculated molar mass of the metal for this trial? 7. What is the percent error in this determination?Explanation / Answer
What is the height of the water column after converting to an equivalent height of mercury in mm?
24.0 mmH2O x ( 1.00mm Hg/ 13.6 mmH2O) = 1.76 mm Hg
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2.What is the pressure of the hydrogen gas in the column in mm Hg?
25PH2OmmHg=23.8
760.00 - 23.8 – 1.76 = 734.44 mm Hg
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3.What is the pressure in the question 2 converted to atmospheres?
734.44 mm Hg x ( 1 atm/760 mm Hg) =0.9664 atm
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4.What is the number of moles of hydrogen gas in the Sample?
N=PV/RT =0.9664 atm* 0.051 L/ [0.0821 x (25+273 k)
=0.002015 mol of H2
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5.What is the number of moles of metal in the sample?
0.002015 mol of H2 x (1mol Mg /1mol H2)=
= 0.002015 mol of Mg
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6.What is the calculated molar mass of the metal for this trial?
0.0500 /0.002015=24.81g/ mol of Mg
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7.What is the percent error in this determination ?
Molar mass Mg = 24.31 g/ mol
= (24.8124.31)/24.31 * 100=2.1
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