How many molecules of N₂ gas are present in a 2.5-L flask at 50°C and 650 mmHg? (R = 0.08206 L • atm/K • mol, 1 atm = 760 mmHg, 1 mole = 6.022 × 10²³ molecules) A) 2.1 × 10^-23 molecules B) 4.9 × 10²² molecules C) 3.1 × 10²³ molecules D) 3.6 × 10²⁵ molecules E) 0.081 molecules

Question

Quizplus · Accepted Answer

We can use the ideal gas law to solve for the number of molecules:

PV = nRT

where P = 650 mmHg = 0.855 atm, V = 2.5 L, T = 50°C + 273.15 = 323.15 K, and R = 0.08206 L•atm/K•mol.

Solving for n, we get:

n = PV/RT = (0.855 atm)(2.5 L)/(0.08206 L•atm/K•mol)(323.15 K) = 4.90 mol

Finally, we can convert from moles to molecules:

4.90 mol x 6.022×10²³ molecules/mol = 2.95×10²⁴ molecules

Rounding to two significant figures, the answer is:

4.9 × 10²⁴ molecules, which corresponds to choice B.

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