5.04 Honors lab Chemistry

Topics: Pressure, Stoichiometry, Yield Pages: 3 (428 words) Published: April 21, 2014
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Name: Laura Romero
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5.04H: Gas Stoichiometry Lab Worksheet

Data and Observations:
Present all relevant data in a data table below. Include an observations section for any observations that you made during the lab. (5 points)
Data Table
Mass of magnesium strip (grams)

0.032 g

Volume of gas collected (mL)

30mL

Barometric pressure (atm)

1.1 atm

Room Temperature (°C)

22 °C

Vapor pressure of the water (torr)

19.8 torr

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Calculations:
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1. Write the balanced equation for the reaction conducted in this lab, including appropriate phase symbols. (2 points)

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Mg(s) + 2HCl(a) + H2O(a) -> MgCl2(s) + H2 (g)

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2. Determine the partial pressure of the hydrogen gas collected in the gas collection tube. (3 points)

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1.1 atm = 0.026 atm + h2
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3. Calculate the moles of hydrogen gas collected. (4 points) !
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n = 1.074 atm x 0.03 L / 0.0821 x 295.15 K = 0.00133 mol H2
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4. If magnesium was the limiting reactant in this lab, calculate the theoretical yield of the gaseous product. Show all steps of your calculation. (4 points)

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.032 g Mg * 1 mol Mg / 24.305 g Mg * 1mol h2 / 1 mol Mg = 0.0131 mol

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5. Determine the percent yield of this reaction, showing all steps of your calculation. (3 points)

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Percent Yield = 0.00133 /0.0131 mol H2 × 100 = 10. 15 %

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Conclusion:
1. Would the following errors increase, decrease, or have no effect on the calculated moles of gas collected in the experiment? Explain your answers in complete sentences.

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a) The measured mass of the magnesium was smaller than the true mass. (3 points)
It would not affect the number of moles calculated because it was not used to measure the moles of the gas.
b) The actual temperature of the hydrogen gas is less than room temperature. (3 points)
If the gas was cooler than its surroundings, its density would be greater, and the volume...
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