app.tophat.com Lecture 1-I Top Hat periodic tabl for m g answ CH10: Gases Fullsc
ID: 714596 • Letter: A
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app.tophat.com Lecture 1-I Top Hat periodic tabl for m g answ CH10: Gases Fullscreen Export PDF Problem Statement: The following reaction was carried out Mg(s) + 2 HCKag)MgCl2(aq)H The hydrogen gas was collected over water, It was observed that 24.3 mL of 20.0 °C water was displaced. The barometric pressure during the experiment was 767.0 mm Hg. At 20.0 C, water has a vapor pressure of 17.5 mm Hg Determine the mass of hydrogen gas produced. Step 1: Determine the volume of gas produced Assigned as Homework O 010.35a Fill in the Blanks What is the volume (in ml) of hydrogen gas that was collected? Fill the unit in the 2nd blank lunit)Explanation / Answer
a)
volume of H2 gas = volume of water displaced by gas
= 24.3 mL
b)
total pressure = 767.0 mmHg
pressure of H2O = 17.5 mmHg
USE Dalton’s law of partial pressure:
pTotal = p(H2O) + p(H2)
767.0 MmmHg = 17.5 mmHg + p(H2)
p(H2) = 749.5 mmHg
Answer: 749.5 mmHg
c)
Given:
P = 749.5 mm Hg
= (749.5/760) atm
= 0.9862 atm
V = 24.3 mL
= (24.3/1000) L
= 0.0243 L
T = 20.0 oC
= (20.0+273) K
= 293 K
find number of moles using:
P * V = n*R*T
0.9862 atm * 0.0243 L = n * 0.08206 atm.L/mol.K * 293 K
n = 9.97*10^-4 mol
Answer: 9.97E-4 mol
d)
Molar mass of H2 = 2.016 g/mol
use:
mass of H2,
m = number of mol * molar mass
= 9.97*10^-4 mol * 2.016 g/mol
= 2.01*10^-3 g
Answer: 2.01E-3 g
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