Determination of Gas Constant Name Date: Section: Pre-Lab Questions 1. A student

Question

Determination of Gas Constant Name Date: Section: Pre-Lab Questions 1. A student following the procedures in this lab exercise collected the following data: 0.0243 mass Mg, g initial syringe volume, mL 1.0 final syringe volume, mL 26.5 barometric pressure, torr temperature, K 754 298 Calculate the value of the universal gas constant, R 2. What would be the volume of hydrogen gas produced by the reaction of 0.0243 g of magnesium metal, collected at 750 torr and 298 K? Use the value of R found in question 1. The results of this experiment are affected by the care with which each step is completed Describe how each of the following errors would affect the calculated value of R. 3. (a) The Mg slid into the HCl in the test tube before the system was sealed off. (b) The room temperature increased by 3 °C between the time that the final volume was measured and the temperature was recorded (c) The MgO coating was not removed before the Mg sample was placed in the HCI (d) The test tube was filled with 4 mL of 0.10 M HCl instead of 4 mL of 1 M HCL 121

Explanation / Answer

Q1

Apply Ideal Gas Law,

PV = nRT

where

P = absolute pressure

V = total volume of gas

n = moles of gas

T = absolute Temperature

R = ideal gas constant

R = PV/(nT)

P = 754 mm Hg

T = 298K

dV = 26.5-1 = 25.5 mL = 25.5*10^-3 L

mol of Mg = mass/MW = 0.0243/24.3 = 0.001

R = (754*25.5*10^-3)/(298*0.001)

R = 64.520 torr-L/(mol-K)

Q2

R = (750*25.5*10^-3)/(298*0.001)

R = 64.17 torr-L/(mol-K)

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