A sample of 7.55 g of He has a volume of 5,520 mL and a temperature of 123°C. What is its pressure in torr?

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Chemistry Sapo 5 years 2021-08-22T18:22:28+00:00 2021-08-22T18:22:28+00:00 1 Answers 103 views 1

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quangkhai · Answer 1 · 2021-08-22T18:24:26+00:00

Answer: The pressure is 8451.2 torr.

Explanation:

Given: Mass of He = 7.55 g

Volume = 5520 mL

Convert mL into L as follows.

$1 mL = 0.001 L\\5520 mL = 5520 mL \times \frac{0.001 L}{1 mL}\\= 5.520 L$

Temperature = $123^{o}C = (123 + 273) K = 396 K$

Now, moles of He (molar mass = 4.00 g/mol) are as follows.

$No. of moles = \frac{mass}{molar mass}\\= \frac{7.55 g}{4 g/mol}\\= 1.8875 mol$

Formula used to calculate pressure is as follows.

PV = nRT

where,

P = pressure

V = volume

n = no. of moles

R = gas constant = 0.0821 L atm/mol K

T = temperature

Substitute the values into above formula as follows.

$PV = nRT\\P \times 5.520 L = 1.8875 mol \times 0.0821 L atm/mol K \times 396 K\\P = 11.12 atm$

Convert atm into torr as follows.

1 atm = 760 torr

$11.12 atm = 11.12 atm \times \frac{760 torr}{1 atm}\\= 8451.2 torr$

Thus, we can conclude that the pressure is 8451.2 torr.