Question 5 (2 points) A student carried out this experiment and found: mass gela

Question

Question 5 (2 points) A student carried out this experiment and found: mass gelatin capsule = (1.26|0x10^-1) g mass alloy sample+gelatin capsule- (2.72x10A-1) g mass empty beaker = (1.449x10^2) g mass beaker + displaced water = (3.012x10^2) g Temperature = 294.15 K Barometric pressure = 746 mm Hg vapor pressure of water = 18.65 mm Hg How many moles of hydrogen gas were produced? Enter your answer in scientific notation with three significant figures. Do not include any units in your answer. Note: The numbers in this problem are different from the numbers in the other problems. Note: Your answer is assumed to be reduced to the highest power possible. Your Answer x10 Answer

Explanation / Answer

Using the ideal gas law, we can determine the no of moles of hydrogen gas produced.

As we know according to ideal gas law

PV = nRT

Here P = P(H2)

n= n(H2) and V and T are volume and temperature of the gas.

Since the H2 is collected over water, gas is mixture of H2 and water.The total internal pressure is equals to barometric pressure and pressure of hydrogen gas is equals to Pbar - Pvap

So P (H2) = Pbar - Pvap

P (H2) = 746 - 18.65 = 727.35 mm Hg = 0.957 atm

R = 0.082057 L atm/mol/K

Now volume of gas is the water displaced by hydrogen so we know

Mass of beaker = 1.449 X 10-2 g

Mass of beaker + Displaced water = 3.012 X 10-2 g

So displaced water = 3.012 X 10-2 g - 1.449 X 10-2 g = 1.563 X 10-2 g or 1.563 X 10-5 L

Temperature = 294.15 K

n = PV / RT

n = 0.957 X 1.563 X 10-5 / 0.082057 X 294.15

n = 1.49 X 10-5 / 24.14

n = 0.06172 X 10-5

n = 6.172 X 10-7 mol

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