Chem IA Molar Volume of a Gas Advanced Study Assignment A student reacts a 0.050

Question

Chem IA Molar Volume of a Gas Advanced Study Assignment A student reacts a 0.050g sample of magnesium in excess hydrochloric acid in order to produce hydrogen gas collected at room temperature (23.2°C .48.6 mL hydrogen gas is collected in an eudiometer tube with water initially at 20.0 C. 1. How many molesof magnesium are reacted? Moles of magnesium reacted: 2. From the balanced chemical equation, how many moles of hydrogen gasare created? Moles of hydrogen gas created: 3. If the pressure inside the eudiometer tube is equalized to atomspheric pressure (1.00 atm) what is the pressure of ONLYthe hydrogen gas in the tube without water vapor? Pressure ofHydrogen gas only: 4. Considering that this reaction was not performed atSTP, calculate the volume of hydrogen gas that would have been produced at STP. (Hint: use equation l) volume of Hydrogen gas at STP. 5. Using the information you calculated, what is the molar volume at STP for Hydrogen gas? Molar Volume of Hydrogen Gas 6. Given the known molar volume of an ideal gas atsTP,calculate the percent error in your experiment Percent Error:

Explanation / Answer

Q1.

moles of Mg reacted:

mol = mass/MW = 0.05/24.3 = 0.00205 moles of Mg,

all of this react since there is excess acid

Q2.

the reaction

Mg(s) + 2HCl(aq) = H2(g) + MgCl2(aq)

find moles of H2 created

mol of Mg =0.00205, mol of H2 = 2*Mg = 2*0.00205 = 0.0041 moles of H2

Q3.

Pinside = 1 atm

find P of H2:

PV = nRT

P = nRT/V = (0.0041)(0.082)(298)/(48.6*10^-3)

P = 2.06 atm due to H2

Q4.

find V of gas:

PV = nRT

V = nRT/P = (0.0041)(0.082)(20+273)/(2.06)

= 0.47 mL

Q5.

find molar Volume of H2 at STP

V = volume / mol

V = 47*10^-3 / (0.0041) = 11.46 L per mol

Q6.

error %= (22.4-11.46)/(22.4) *100% = 48.8%

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